The Perfect Corner RulerTM
The Perfect Corner MethodTM

Making Pieced Corner Triangles PerfectTM


Using the Perfect Corner Ruler™ & Perfect Corner Method™

These are the steps for the Perfect Corner Method™. The steps are in detail so that they can be followed by those who have never pieced a corner triangle before. There are the same number of steps in the Perfect Corner Method™ as there are in the "Sew & Flip" method. The following steps show how the Perfect Corner Method™ is used with thousands of existing patterns that have been written for the problematic "Sew 'N Flip" method.

Perfect Corner Method™ "Sew & Flip" Method
1. Draw the sew line. 1. Cut the corner square.
2. Cut the fill-in square & cut in half on the diagonal creating two corner triangle. 2. Draw the diagonal sew line on the corner square to yield one corner triangle.
3. Pin right sides together and sew on the line. 3. Pin right sides together and sew on the line.
4. Press into corner & square. 4. Press into corner - stuck with results.


1. The Perfect Corner Ruler™ is placed along the edge of the wrong side of the block [Base Unit] needing to have its corner replaced with a triangle. Since we are using the reverse / wrong side of the block the corner is also reversed [i.e. we are working on the top left corner, which means the change is to the top right corner on the right side of the fabric]. Locate the size of the corner triangles called for in the pattern [in this example it is 2"] on the black ruling Sew Inch markings on the Perfect Corner Ruler™. Allign the triangle at that ruling with the edges of the wrong-side of the Base Unit, as shown. Draw the sew line on the wrong-side of the Base Unit along the long side of the triangle [the hypotenuse].

2. Cut a fill-in square that to the size shown in teal with the cut block icon on the ruler next to the Sewing Line Inch that was used above. In this case, the Sewing Line Inch was 2" so the fill-in square will be 2 3/4". 

And, cut the fill-in square in half on the diagonal. This provides two corner triangles per corner square. This saves you fabric. This is because even though you will be cutting the fill-in square slightly larger than the pattern's corner square [3/4" larger, to be exact], you will cut half as many fill-in squares [and related strips] than the patterns requires, saving fabric!

3. Place one of the Corner Triangles right side up underneath the Base Unit, which is wrong side up, as shown. The right sides will be together and the wrong side of the Base Unit will be up so that you can see the sewing line. "Eyeball" that approximately ¼” of the Corner Triangle extends beyond the sewing line for the seam allowance. The "dog eared" corners of the Corner Triangle should protrude from beneath the Base Unit equally, as shown.

Sew directly on the sewing line. Since you will be starting sewing with the presser foot on the corner triangle fabric, it will not pull it into the throat plate of the sewing machine, as often happens with the "Sew 'N Flip" method.

4. Press into the corner with the seam allowance away from [left] or towards [right] the corner. Align a square ruler to the original size of the Base Unit and trim off the excess Corner Triangle fabric [some use the Perfect Corner Ruler™ for this, but that only squares in relationship to two sides of the base block and thus can lead to allignment errors].

We always finish by folding the Corner Triangle down out of the way, underneath the Base Unit, and trim the excess Base Unit fabric to the ¼” seam allowance. This saves fabric as we are discarding only one triangle versus the two that are discarded using "Sew & Flip". To be fair, we did not list this as a step for "Sew & Flip" either, although it always is done.

Watch the video.