Monday, September 28, 2026

City Line QAL - Week 2

Graphic with photo of 8 blue fabrics in the background and a digital mockup of the City Line Quilt in the foreground.  Text reads "City Line Quilt Along, Sept.21 - Oct.26, 2026.  Week 2".
City Line pattern available here

Week 1

Welcome to Week 2 of the City Line QAL. Last week we cut fabric.  This week’s task may seem short, but I recommend lots of pinning for it.  Pinning always seems to take forever, so I decided it was enough work for one week.  After all, I promised an easy pace!


Sort the Strips

First, flip back to page 1 of the pattern and sort your eight colour fabrics from dark to light as described in the lower right quarter of the page,

8 strips of assorted blue fabrics, sorted from dark to light, with the darkest on the left.
Thank you to White Owl Textiles for sending me
 these fabrics from their Fundamentals collections. 
Scroll to the bottom of this post for additional fabric details.

Next pair each darker fabric with a lighter fabric.  Since you’ve already cut your strips, you can put one strip of each fabric up on your design wall, or simply lay them on a table, and shuffle them around until you like the pairs.  Just remember that each pair needs contrast, and keep the darker fabric in the pair on the left.

8 fabric strips in 8 different blues, divided into 4 pairs.  Each pair has the darker fabric in the pair on the left.  Pairs are lined up left to right.

You can see I did not adhere strictly to the instruction to pair each of the four darkest to one of the four lightest.  My darkest was much darker than the darkest light fabric, and I didn't want quite that much contrast, so I shuffled things a little more. I ended up using my darkest dark and fourth darkest dark together, and the darkest light became a "dark" paired with the lightest light.

All to say, just go ahead and shuffle those fabrics until you have an arrangement that you like, keeping the darker fabric in each pair on the left.  Also, I chose to repeat each fabric pair three times to use up all 24 strips, but you could shuffle all 24 strips for more varied pairs.  

I recommend pinning a numbered label to each strip to keep track of your fabrics once you have them ordered as you like.  I just counted 1 to 8, and repeated.  If you chose to shuffle all 24 strips, you can label them 1 to 24 to keep track of their order.

8 fabric strips in 8 different blues, divided into 4 pairs.  Each pair has the darker fabric in the pair on the left.   Pairs are ;aid out side by side, with fabrics labelled 1 to 8 from left to right.

Sew Strip Pairs

Now flip ahead to page 4 and proceed with steps 1 and 2.

Step 1 is where all the pinning happens.  Matching the ends and the centers of the strips is key to ending up with a straight strip pair unit with nice even ends.  This will also help ensure all your strip pairs will be the same length, which will result in a clean, straight panel later.  Refer to this tutorial for more guidance on matching and pinning strips.

Step 2 is short but important.  Pay attention to the pressing directions. Paired with other pressing direntions in Week 4, these will allow you to nest and spin seams in the center pieced strip.

Here are my strip pairs, all sewn, with seams pressed towards the even-numbered fabrics, ready for next week.

24 fabric strips, 3 each of 8 fabrics, side by side in pairs.  In each pair, the darker fabric is on the left.

I'm excited to see what your pairs look like.  Did you make eight pairs and repeat, or did you shuffle all the fabrics in more combinations?  Remember you can share on social media (make sure to mention the City Line QAL in your post or #citylineqal), you can email me, or you can share in the Quilting With Canuck Quilter Facebook group.


Happy sewing,

Joanne

PS:  It's not too late to join in this six-week quilt-along.  Purchase the pattern (if you don't already own a copy) then follow along with the weekly blog posts I'll publish every Monday.  If you'd like to have the links delivered directly to your inbox to avoid having to search for them, or if you'd like to make one of the bonus sizes (twin, full, queen or king) currently exclusive to the QAL, you can register for free here.

8 blue or aqua fabric laid out over a grey fabric.  Each fabric is labelled with the manufacturer's SKU.  Additional text reads "Fabrics were contributed byWhite Owl Textiles for Lumin Fabrics"
Fabrics for my version contributed by White Owl Textiles



Friday, September 25, 2026

Matching ends and centers when sewing long seams

I avoid pinning when I can get away with it, but sewing long seams is not one of those times.  

Two strips of blue fabricsewn togeter, with a pincushion to one side and loose pins on the other side.

The top or bottom fabric may shift a tiny bit relative to the other fabric every time the feed dogs advance the fabrics.  It's usually such a slight shift that it's not noticeable over short seams.  In longer seams, it adds up so that one fabric seems longer than the other, even when they were the exact same length when you started. 

Closeup of two pieces of blu fabric sewn together, highlighting that one of the pieces is slightly longer than the other.

Even if it's a small difference, it makes it harder to piece accurately when you add this unit to another part of the quilt.  That small shift of layers can also add a slight bend in a strip set, or a ripple in the seam.  Sorry I couldn't get a good photo of that, but I'm sure many of you have experienced that firsthand.

The key to avoiding this is to match and pin the two pieces you're sewing together.  I'll demonstrate with strips, but this works for any two edges that are the same length.  You could be sewing a strip to a larger pieced section, or adding a measured border to the side of a quit.  (Check out this tutorial for more on borders.)


Step 1:  Start with two strips of equal length.

Two strips of different blue fabric side by side.


Step 2: Fold one strip in half right sides together and the other strip in half wrong sides together.  Crease the folds to mark the center of each strip.

Two strips of fabric, each folded in half end to end..  The top one is folded right sides together, the bottom one is folded wrong sides togetyer

When you unfold them and look at them both right side up, you will see the creases created a little valley in one and a little hill in the other.

Two blue fabric strips showing the creases where they were folded.  The crease in the top one forms a valley, the crease in the bottom one forms a hill.
Valley in the top strip, hill in the lower one.

Step 3:  When you lay the fabrics right side together in preparation for sewing, the creases in the two pieces should nest.

Two strips of fabric layered together, offset to show how the creases in the strips nest together

Of course you'll also need to line up the edges where the seam will be sewn, but I wanted to show you how the two creases nest so had to pull the top fabric down so you could see both fabrics.


Step 4:  Pin center and ends.  

Pin the centers together by pinning in the nested crease.

Match the right ends of the strip and pin in place.  Repeat at the opposite end of the strips.

Fabric strip with a pin at each end and nother in the center


Step 5
:  Add more pins between these to keep the fabric layers from shifting between the pins.  I like to add a pin every 2" to 3". 

Fabric strip with  7 pins inserted at regular intervals

If there's a fair distance between the center and the ends, I start by pinning halfway between the center and end pins, then halving that distance with another pin, repeating until everything is pinned every 2" to 3".


Step 6:  Sew the strips together, taking care not to sew on a pin.  

Hand guiding fabric strips under the needle of a sewing machine

I don't remove all the pins as they near the needle, because then there wouldn't be anything keeping the layers from shifting.  However, I do slow down when I get close to the needle, and slip the pin out immediately in front of the needle, as close as I can get, if it looks like the needle might hit the pin instead of dropping in front of or behind it.

Here is the strip pair, with a ruler to show it's straight and the ends of the original strips are even with each other.

Strip setmade of two blue fabric, undser a quilting ruler to highlight the strip set is straight and has straight, even ends

Closeup of the left end of a strip set made of two blue fabric, under a quilting ruler to highlight the strip set is straight and has straight, even ends

Closeup of the right end of a strip set made of two blue fabric, under a quilting ruler to highlight the strip set is straight and has straight, even ends

That's all there is to it.  It's a little more time consuming to pin than not, but in the case of longer strips it really helps me piece more accurately for a tidy result.

I'd love to know your top tips for sewing long seams.  Please share them in the comments.

Happy sewing,

Joanne

Thank you to White Owl Textiles, a division of Lumin Fabrics, for sending the fabrics I used in this tutorial.  These are from the Fundamentals collection "Codici".


Monday, September 21, 2026

City Line QAL - Week 1

Grpahic with photo of 8 blue fabrics in the background and a digital mockup of the City Line Quilt in the foreground.  Text reads "City Line Quilt Along, Sept.21 - Oct.26, 2026.  Week 1."

It’s time!  The City Line QAL kicks off today.  For the next six weeks we’ll be sewing the City Line quilt.  I’ll break the pattern into six easy parts, one per week, to set an easy pace.  I’ll share tips and tutorials along the way here on the blog.

If you’re already registered and have your pattern, you’re all set.  You can skip ahead to the next paragraph.  If you still need to purchase the pattern, you can find the PDF download version here.  Registering gives you access to the bonus quilt sizes not included in the pattern and adds you to the email list to receive the links to the blog posts and tutorials so you don’t have to look for them every week.  You can register for free here.


QAL Week 1 - Cut fabric

This week, skip over page 1 to the cutting instructions on page 2.  The pairing and numbering of fabrics can wait until next week (unless you have already done that, in which case, yay you!).  The labelling of fabrics won’t affect how many strips of each fabric you need, as you cut the same number from each fabric.  In adition to the instructions in the pattern, read on for extra guidance, tips, and links to helpful tutorials.


Cutting Non-Background Fabric

When cutting the strips of non-background fabrics, pay particular attention to two things.

1. Make sure the strips are straight.

Cut the strips to avoid an angle or bend in the middle.  You need all the strips to fit together smoothly. A bend in any of them would interfere with that.

Two cut fabric strips on a cutting mat with rulers, showing the strip on the left is bent and the strip on the right is straight

For guidance on how to avoid the bend, refer to my new tutorial on cutting strips.

2. Cut all the strips to the same length. 

8 fabrics strips in assorted shades of blue, side by side to show they are the same length.
Thank you to White Owl Textiles for sending me
 these fabrics from their Fundamentals collections. 
Scroll to the bottom of this post for additional fabric details.


I know it’s tempting to sew strips together willy nilly, then trim the sewn unit to size, but that could introduce some bowing in the strip set. We won’t be sub-cutting these sets into smaller units, so there will not be any opportunity to mitigate bowing in the strip sets at that step, as there often is when cutting strip sets into smaller units. Starting with strips exactly the same length is key to keeping things straight now so you have have straight units to make your center panel later.   Also, the strip sets will become columns, and you need them all the same length unless you plan to redo all the math for the background pieces.

I prefer to cut the strips to length right after cutting them, before I unfold them.  Refer to my new tutorial about cutting strips longer than your ruler for guidance on measuring long strips.


Cutting Background Fabric

Cut Wide borders (B and C)

The top and bottom borders may be wider than your ruler, especially if you are making one of the larger bonus sizes of the quilt.  This tutorial shares how I tackle those wide cuts.

These come up first in the cutting chart, even though they get used last when assembling the quilt,  because I like to cut the largest parts first.  If I goof there, I can cut smaller parts from the large oops parts, and hopefully be able to recut the miscut part from the remaining fabric. 


Cut setting pieces (D to J)

As much as possible, I cut pieces in decreasing size order, but there are exceptions.  To make most efficient use of fabric, I cut as many large pieces as possible from a strip, then find smaller pieces that can be cut from the remaining strip length.  Sometimes that means skipping a few in-between sizes, or cutting lots of smaller pieces individually here and there instead of all at once from one strip. To save you the trouble of figuring this out, I have added a cutting diagram to the cutting instructions in the pattern showing which pieces D to J can be cut from each background strip.

Cutting diagram for background fabric: rectangle subdivided into smaller squares and rectangles, each one labelled with a part of the City Line quilt, showing how to cut all the parts from the yardage.

You’ll notice that it ends up skipping from D directly to F in one strip, and from E to H in another, and that not all H are cut at once.  It’s not a problem.  The important part is to end up with the correct number of each piece in the end.  

Also note that my cutting charts and diagrams are based on 40" width of fabric.  If your fabric is wider, you might be able to squeeze additional parts from some strips and reduce the total number of strips you need to cut.

I recommend labelling the different size setting pieces for quick identification when you need them later. You can use fancy alphabet clips.  You can grab a sharpie and label some wonderclips.  You can do what I do and just cut up squares of scrap paper, write the part labels on them, and pin them to the top of each stack of parts. (Now that I've thought of the sharpie/wonderclip combo, I might do that next time.  It's not like I can't use the clips for binding just because they have letters on them!)

Fabric parts for the City LIne quit cut out and stacked, with grey setting pieces labelled D through K.


That’s all for this week.  Go forth and cut fabric!  We’ll reconvene next Monday to start sewing.


Happy sewing,

Joanne

8 blue or aqua fabric laid out over a grey fabric.  Each fabric is labelled with the manufacturer's SKU.  Additional text reads "Fabrics were contributed byWhite Owl Textiles for Lumin Fabrics"
Fabrics from White Owl Textiles


Cutting wide strips with a narrow ruler

If you piece quilts with wide borders or large areas of negative space in the background, you have probably encountered the need to cut a width-of-fabric strip that is wider than your widest ruler.  Cutting large squares to cut setting triangles when setting blocks on point also often requires wider cutting.  What's a quilter with narrow rulers to do?

I have two methods to share with you.  For either method you'll need to start with a straight edge.  

Note:  I'm right handed so these instructons are right-handed.  If you are left-handed you'll need to reverse left/right directions.

Straighten the cut edge of the fabric

Fold the fabric in half along the length, selvedge to selvedge. 

Position the fabric with the edge to straighten on the right.

Lay your ruler over the fabric to extend across the entire width of fabric, from fold to selvedges, lining up a horizontal measurement line with the fold (highlighted as a red line in picture below).  The precise measurement doesn't matter.  You just want a straight line aligned with the fold.  That will give you the 90 degree angle at the corner where the fold and the ruler's side meet.

Grey fabric on a cutting matt.  Fabric is folded selvedge to selvedge, with the fold at the top of the photo.  A rotary cutting ruler extend from the beyond the fold to beyond the selvedge, with the right side of the ruler positioned just to the left of the edge of the fabric.  A red line highlights how a horizontal measurement marking on the ruler is lined up with the folded edge.  A rotary cutting ruler stands by.

Trim along the right side of the ruler.  You should now have a cut straight edge that is perfectly square with the folded edge.

Grey fabric on a cutting mat.  Fabric is folded selvedge to selvedge, with the fold at the top of the photo.  A rotary cutting ruler extend from the beyond the fold to beyond the selvedge, with the right side of the ruler flush with a straight, clean cut edge, with a skinny ragged strip of fabric that has juts been cut away on the right. Red lines highlight the 90 degree square corner where the fold meets the cut edge.e.

Turn the fabric or rotate the cutting mat 180° to position the straightened edge on the left.


METHOD 1

In this example, I'm cutting a 11"-wide strip.  The 6" width of my 6" x 24" ruler is clearly not wide enough.  I can turn the ruler 90° and use the 11"  measurement.  (You may notice I swapped my 12" ruler for the 24", because it's less cumbersome but still long enough.  If I needed to cut a strip wider than 12", I'd stick with the longer ruler.)

Gray fabric in a cutting mat.  Quilting ruler placed on top to measure 11" away from left edge of fabrc.  REd markings highlight the measurement markings and the 90 degree corner where the cut edeg of the fabric and the fold  in the fabric meet.

As always when measuring strips, I make sure a horizontal marking aligns up with the folded edge, and the measurement I'm cutting (11" in this case) lines up with the straightened cut edge.

The ruler doesn't span the distance from fold to selvedge.  That's OK.  I cut along the right edge of the ruler, stop before I run out of ruler, move the ruler up, again measuring 11", and cut again.  I repeat that until I've cut all the way up to the selvedge.

Grey fabric being trimmed to a specific width.  Rotary ruler is positioned on fabric and rotary cutter lies beside it where the fabric has been trimmed

Grey fabric being trimmed to a specific width.  Rotary ruler is positioned on fabric and rotary cutter lies beside it where the fabric has been trimmed

Grey fabric on cutting mat, with extra fabric trimmed away from the right side.

I now have a 11" strip, ready to use for borders, or subcutting, or whatever the pattern calls for. 

What if you don't have a ruler long enough for the width?  See Method 2 below.


METHOD 2

This method pairs multiple ruler to add up to the required measurement.  In this example I'm cutting an 8.5" strip.  I could have cut this using Method 1, but I wanted to demonstrate Method 2. The smaller scale is easier to photograph to show detail, so I'm demonstrating with a 8.5" strip width.  This method would be most useful when you don't have a long enough ruler to use Method 1.

There's a tiny bit of math next, but it's simple arithmetic so even if you're not fond of math, don't panic.

Subtract the width of one ruler (let's call this Ruler #1) from the required strip width.  In this case I'm using my 6" x 24" ruler to span from fold to selvedge, so the width is 6".

8.5" - 6" = 2.5"

The resuting number, 2.5" in this example, is the measurement to use with Ruler #2.  I position my Ruler #2 to measure 2.5" from the cut edge.

grey fabric on cutting matt, with ruler positioned to measure 2 1/2" from the left edge.  A red double-ended arrow highlights the measurement.

Next, I tuck Ruler #1 up against this one, on the right, over the fabric.. The measured 2.5" on Ruler #2 plus the width of Ruler #1 on the right add up to the required 8.5".

Tow ruler combined to measure an 8 1/2" width.  One ruler is positioned so the right side is 2 1/2" away from the left edge of the fabric.  The second ruler is tucked against the first ruler.  The width of the second ruler plus the 2 1/2" of the fisrt ruler add up to the desired measurement.

When using a longer ruler on the right, I have the option of sliding the left ruler up along the right ruler before I cut, making sure to not move the right ruler, to double check that the edge is square and the width measurement will be accurate all the way up to the selvedge.

Two ruler stacked side by side over grey fabric to measure a wider width.

Uusing a 24" long ruler on the right I can cut along the right edge and be done.

Newly cut wide strip of grey fabric on a cutting mat.  Rulers used to measure are still in place over the fabric and the rotary cutter lies to the right side.



If my ruler was shorter I could cut, move both rulers up, and cut again, as in Method 1.

Which method do your prefer for cutting wide strips?  Please share your tips and suggestions in the comments!

Happy quilting,

Joanne

PS: This fabric used in this tutorial is "Smoke" from the Codici collection, one of White Owl Textiles' Funadamentals collections, their colour basics.   I love the Codici dots!



Sunday, September 20, 2026

Cutting strips longer than your ruler

What do you do when you need to cut a piece that is longer than your ruler?  You fold the fabric and do a little math.  It's a tiny little bit of math, easy peasy, I promise.

Any ruler can be used to cut a piece that is up to twice as long as the ruler.

·         A 24” inch ruler will allow you to cut lengths up to 48” long.

·         A 12” ruler will allow you to cut lengths 24” or shorter.

As an example, let's cut a 2.5" x 18" strip with a 12" ruler.  I'm demonstrating using a 12" ruler to demonstrate the technique because it's easier to photograph and show details when using the smaller ruler, but this applies to any length up to twice as long as the ruler you have available.


Preliminary Steps

Step 1: Calculate half the required length.  Let’s call this H.

For my example:  half of 18" is 9", so H=9".

Step 2: Cut a strip to the required width. (Refer to this tutorial if you need guidance on measuring and cutting straight strips.)


Make a Decision

At this point you need to decide if you prefer two smaller scraps leftover, or need one longer scrap. 

Fabric strips on a cutting mat.  A dark strip and a short strip are the same length and are each labelled "measured strip".  One dark strip is shorter than the measured dark strip.   Two light strips are the same length bit shorter than all the other strips.

For example, if I'm cutting 38" strip from a 40" strip, I can end up with two 1" scraps or one 2" scrap.  Do I need that 2" piece or can I live with two 1" pieces to discard?  I'll probably live with the 1" bits.

In a different scenario, suppose I'm cutting a 28" piece from a 40" strip.  I might need the full 12" leftover to cut one 8" piece and one 4" piece as well.  Two 6" scraps won't let me cut both those extra pieces.

I know that looks like math.  The easiest thing to do is buy extra fabric so you deal with the two extra scraps, save them for another project, and cut the extra pieces from extra fabric.  However, that costs extra fabric, and only you know if that's in your budget so I'm giving you options!

I'll show you what to do in each cae.  Remember that in the examples below, I'm cutting 18" strips using a 12" ruler.


OPTION 1 - Two Shorter Scraps

Step 1: Fold the strip in half. (If you cut the strip from a piece of fabric folded selvedge to selvedge, just don’t unfold the strip.)

Step 2: Position your ruler square with the fold, with measurement H on the fold.

Long strip of blue fabric folded selvedge to selvedge, on a cutting mat.  A cutting ruler is positioned over the strip, with the desired measurement aligned along the fold.  An arrow points to the measurement line, and the text reads "H=9 measurement line aligned with the fold in the strip".

Step 3:  Trim away the ends of the strip extending past the end of the ruler

Blue strip trimmed to deisred length, with rulers still in position.  Ends that were trimmed awa lay to the right of the trimmed strip.


When you open up that fold you should have a piece the length you needed, plus two extra scraps trimmed from the ends.

Trimmed strip and the two scraps resulting from trimming the strip to length.


OPTION 2 - One Longer Scrap

Step 1:  Fold the strip so the length of the top layer is just a little longer than H.  You could try to make that top layer exactly H, but that's a little fussy to do.  Going a smidge over H gives you wiggle room.  I like wiggle room. In the photo below the wiggle room is extra generous because there's unusable selvedge at the end of that top piece, so I'm extending it past H so that bit will be trimmed away too.  

Blue strip of fabric on a cutting matt above a quilting ruler and rotary cutter.  The strip is folded back on itself, with the fols on the left.

Step 2: Position your ruler square with the fold, with measurement H on the fold.

Rotary cutting ruler positioned over a foled strips of fabric, with the ruler positioned to measure from the fold in the fabric.

Step 3:  Trim away the ends of the strip extending past the end of the ruler.  (I just noticed I swept the little trimmed bit of selvedge off before I took the picture below.  It was trimmed, trust me!)

Foled trimmed fabric strip still under the ruler used to measure and trim the strip, with the long scrap strip that was trimmed away lying to the right.

When you open up the fold you should have a piece the length you needed, plus one scrap trimmed from the end.

Unfolded trimmed strip, with leftover scrap, rotary cutter and ruler below it

That's all there is to it!  

As always, please drop your questions or anything you'd like to add in the comments below.

Happy quilting,

Joanne

PS:  Thank you to White Owl Textiles for the fabrics used in this tutorial. Both are from their "Codici" Fundamentals collection.

  • Option 1:  Denim (W165-001-555)
  • Option 2:  Navy (W165-001-585)

Friday, September 18, 2026

How to cut straight strips

One of the most useful skills I have learned in rotary cutting is how to cut straight strips from selvedge to selvedge.   You can make most efficient use of your fabric if you don't have to discard the middle of the strip becase there's a little jog or bend in the middle.  Also, discarding the middle bit isn't an option if you're making width-of fabric strip sets, or when you need a strip longer than half the width of fabric.

Two blufbaric strips on a cutting mat with rulers highlighting the strip on the left is bent while the strip on the right is straight

I purposely cut the bent strip shown above a little more crooked than you would probably usually see, to make sure you could see the bend in the photo.  Less pronounced jogs in your strip are still a problem though.  Read on for my best tips to avoid them.

I strongly recommend using a 24” ruler.  The ruler will be long enough to span most quilting cottons when folded in half selvedge to selvedge.  You could fold the fabric into four layers so a shorter ruler could span the width, but I have not had good results this way.  I don't have eyes on that inner fold to make sure it's straight with the ruler to avoid a bend when cutting through that fold.


Step 1: Fold the fabric

Fold the fabric in half, selvedge to selvedge, matching the selvedge edges.  Check the folded edge to see if it's smooth.  If not, slide the two selvedges in opposite directions, keeping them even with each other, until the folded edge is smooth, with no pulling or wrinkles.

Piece of blue fabric folded selvedge to selvedge, with rumpled folded edge
Rumpled fold

Piece of blue fabric folded selvedge to selvedge, with smooth folded edge
Smooth fold after sliding the selvedges 

At this point, you may prefer to straighten the cut edge of your fabric before cutting a strip.  I prefer to straighten that edge after cutting the strip, so I don’t have to reposition the fabric for measuring and risk having the fabric layers shift.  Keep reading.  It will make sense.  I took photos to show you what I do.

Note that I’m right handed, so these instructions and photos show fabric and ruler positions for right-handed cutting.  If you’re left-handed, you’ll most likely need to reverse those.

Step 2: Position the fabric

I prefer to place the fabric on the cutting mat with the folded edge positioned closest to me.  This makes it easier to look straight down at the fold to line up the ruler accurately along the fold to make a straight cut.

Step 3: Place the ruler

Lay the quilting ruler across the fabric, extending beyond the fabric on both ends, with a horizontal measurement line matched perfectly with the folded edge.

Hand positioning a quilting ruler on blue fabric, with an arrow pointing to a horizontal measurement line lined up with the fold in tha fabric.  Text below arrow reads "Horizontal ruler markings are lined up with the fold".

          

Position the measurement line for the width you need slightly to the right of the unstraightrened edge.  Make sure to also keep the horizontal marking lined up with the fold.

Ruler on fabric, with a red line highligting the 2 1/2" measurement markings on the ruler.  the red line is just to the right of the ragged cut edge of the fabric
Rule positioned to cut a 2 1/2" strip. 
The 2 1/2" vertical measurement is highlighted in red.
Notice folded edge is till aligned with a horizontal line on the ruler.

Closeup of a quilting ruler on blue fabric, with a red line highlighting the desitred measurement to the right of the ragged edge of the fabric.
A closer look at the vertical alignment

Cut along the right side of the ruler.

Blue fabric on a cutting mat.  Ruler is in position, and fabrics has been cut along the right side of the ruler and has been pulled away.  Rotary cutter is lying shut on the fabric after the cut.

You could straighten the crooked edge now, but I prefer to cut additional strips first, since there is now a lovely straight edge to measure from for any additional required strips

Multiple strips of blue fabric on a cutting mat.  The leftmost strip has a ragged edge.  The two center strips are straight and even.  The last strip is a wider leftover piece of the fabric. In all strips, the folded center is at the bottom of the photo.


After cutting as many more strips as needed or as many as you can fit on the cutting mat, rotate the cutting mat 180 degrees.  I prefer to rotate the cutting mat rather than manipulate the fabric and risk having the fabric shift before I’m done trimming the strip.  



Position the ruler over the first strip you cut to measure the strip width from the straight edge.

A ruler is positioned over a blue fabric strip, with the 2 1/2" measurement markings lhighlighted in red and positioned along the straight left side of the strip.  The ragged right side of the strip extends past the right dge of the ruler.

Trim away the crooked edge to the right of the ruler. 

Ruler and rotary cutter with trimmed strip of fabrics, showing ragged piece trimmed away from strip when starightening strip.

Also note that if the left edge stops being square with the fold at any time while I'm cutting strips, I prioritize matching the horizontal ruler markings with the fold rather than vertical ones with the left edge.  The strip will not be a consistent width, but as long as I make sure that the narrowest part is at least the width I need, I can trim the strip to the required consistent width after I rotate the mat, in the same way as I trim the strip with the crooked or ragged edge.

Here's one of the strips, unfolded, I zoomed in on the fold, so you can see there is no angle in the sides of the strip at the fold.  It's a tidy straight strip. I'll press that fold out now that I've shown you it's straight where the fold was.

Closeup of fabric strip on a cutting mat, focused on crease where strip was folded, showing there is no bend in the strip where it was folded duting cutting.

That's it! It's simple, but makes such a difference for accurate piecing.  Let me know in the comments if you have questions, or any useful tips to add.

Happy quilting,

Joanne

PS:  Thank you to White Owl Textiles for the fabric used in all but one photo in this tutorial. It's Denim (W110-001-515) from their Fundamentals collection "Stucco".  The first picture showing a bent versus straight strip is from my stash, because I didn't have enough of the Stucco to intentionally miscut a bent strip!