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Using a 12½” square ruler to create the perfect string pieced triangle


I’m so glad that you’re back to check out today’s project! Yesterday on QUILTsocial I demonstrated how to use HEIRLOOM Assorted Plastic Templates to cut applique shapes and we made a cute little bear block. Today’s post is all about rulers!

One of the go-to rulers that I have in my collection is the OMNIGRID Ruler – 12½” x 12½”. This great ruler can be used for cutting and squaring, and has both right and left hand numbering. The black and yellow double sight lines are great for easy viewing when working with light and dark fabrics.


A 12½" x 12½" OMNIGRID Ruler is great for cutting and squaring and can be used by both right and left handed sewers.
OMNIGRID Ruler – 12½” x 12½”


There are two reasons why I like this ruler.

The first reason is that it measures 12½” square. Any ruler that has an extra ½” is my friend. That extra ½” makes it so much easier to square off a block since many blocks (especially those in block exchanges) are 12½” unfinished.

The second reason why I like this particular ruler is because it has a nice long diagonal line from corner to corner. There are two benefits to that diagonal line:

  1. You can use the diagonal line to help square off a block by lining it up with seams in the center of a block as shown below:


The diagonal line of the OMNIGRID ruler goes from corner to corner and assists in the squaring of a quilt block.
Using the diagonal line to help square a block


2. The second benefit is that it is great for cutting right angle triangles from both wide and narrow fabric strips.

Here’s how I use the 12½” square ruler when working with leftover 2½” strips such as those from bindings and jelly rolls.

Note: You can use any strip width you wish. Any width you use will make a great quilt block and will result in a fun quilt. Just make sure that the strips that you use for your block are all the same width to start with.

To make our block today, we’re going to use 2½” strips. Sew four strips together in a step-wise fashion as shown in the following picture.


Four strips of fabric which are all the same width are sewn together in a step-wise fashion to reduce fabric waste when cutting the triangles.
Strips sewn in a step-wise fashion


Line up the OMNIGRID ruler’s diagonal line with the bottom edge of the your strip set.


The OMNIGRID ruler is placed on the sewn strip set with the diagonal line placed along the bottom edge.
Diagonal line of the ruler aligned with bottom edge of strip set


When ready, make your first cut along the side of the ruler to remove the step-wise edge of your strip set. Go boldly, and just do it!

You can see that by sewing the strips together in a step-wise fashion there is less wasted fabric when you trim.


The first cut of the strip set is made using one of the OMNIGRID ruler's edges as a guide.
The first cut


After your first cut, slide the ruler over and place the ½” line along the side that you just trimmed. The diagonal line is still lined up along the bottom of the strip set.


The ½" line on the OMNIGRID ruler is placed along the trimmed side of the strip set with the diagonal line on the ruler lined up along the bottom of the strip set.
The ½” line placed along the trimmed side


Next, cut along the other side of the OMNIGRID ruler to make your first triangle. Continue along the strip set to cut more triangles. You’ll need to flip the ruler over to cut each consecutive triangle. Always make sure to line up the bottom edge of the strip set with the diagonal line on the ruler.


The OMNIGRID ruler was flipped then the diagonal line was aligned with the bottom edge of the strip set and the ½" line was lined up with the cut edge in order to cut the next triangle.
Flip the ruler over to cut each consecutive triangle.


When you’ve cut four half square triangles you’re ready to assemble a block. Sew the triangles together on their square angle. As you can see, putting four triangles together in this way gives you a gorgeous quilt block!


The four striped triangles cut with the OMINGRID ruler are assembled into a beautiful quilt block.
The completed block


The completed block measures 16½” x 16½” and it was easily achieved using the OMNIGRID Ruler – 12½” x 12½”.

This block is VERY versatile!! Sew together four rows consisting of five blocks each and you’ll have a single size quilt top in no time flat! Even better, sew together five rows of five blocks each to create a double size quilt.

The possibilities are endless with this block.

Thanks for joining me today and come back tomorrow when I’ll show you how to make a 3D block!


This is part 3 of 5 in this series.
Go back to part 2: Fussy cutting made easy with assorted plastic templates from Heirloom

Go to part 4: Easy 3D quilt blocks with the SEW EASY Half Diamond Ruler

I took my first quilting course in September 1994 in Barrie, Ontario, near the armed forces base where I was stationed. After moving to Ottawa in 1996, I joined my first guild. I took more courses and began to buy quilting books and lots of fabrics. Quilting has become my passion. I have made over 150 more quilts since then, and have never looked back. I now share my knowledge of quilting by teaching and doing presentations, and blogging!


  1. Johanna

    Great tip to sew the strips in a step-wise fashion to reduce waste. I’m definitely going to do that in the future! Thank you, Paul!

  2. MaryBeth Little

    I love my 12.5″ ruler too. It’s so versitile and useful.

    • I show no preference, I love all my rulers but i do have a little more love for my 12.5″ one (depending on the day).

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