The Perfect Corner RulerTM
The Perfect Corner MethodTM

Making Pieced Corner Triangles PerfectTM


Story Board - General - In Detail

This is a very detailed step-by-step display of the use of the Perfect Corner Ruler™. This storyboard is aimed at providing information for pattern designers and trainers.

General Perfect Corner Ruler Storyboard 300

Talking Points To General Storyboard

Corner Ruler™ will produce accurate corner triangles and save fabric as compared to the common “Sew ‘n Flip” method. Corner triangles are used in snowballs, square-in-a-square, star points, flying geese, flowers, and more.

In this storyboard, the blue fabric is for the base block, and the red fabric is for the corner triangle.


1.      A “Sew ‘n Flip” pattern will specify the size of the corner square to use [in this case 2¼”]. We use that measurement for the size of the corner triangle that is needed. [Note: Using the “Sew ‘n Flip” method one draws a diagonal sew line on the corner square, sews on the line, trims off the two unused triangles {one from the base beneath and the other from the corner square on top} to the seam allowance, and then flips the remaining triangle back into the corner. The triangle often does not fill out the corner to the original size of the block.]

2.      Align the Perfect Corner Ruler™ on the wrong side of the base to the size of the corner triangle needed, in this case 2¼”. Note that you are working on the wrong side of the base and thus the right corner triangle appears on the left side of the wrong/back side.

3.      Draw a sewing line on the wrong side of the base across the edge [hypotenuse] of the Perfect Corner Ruler™.

4.      Now we need to determine the proper size of the corner square so that we will have enough fabric to make two corner triangles and have enough of each so that they can be trimmed down to the intended size of the base. This measurement is listed on the Perfect Corner Ruler™ in teal [in this case 3”] with the divided block icon, next to the measurement that you used to draw your sew line [in this case it was 2¼”].

5.      Cut your corner square to the size indicated [in this case 3”] and cut it in half diagonally.

6.      Place one of the corner triangles right side up underneath the base so that the edges of the corner triangle stick out equally on each side of the base and there is about ¼” seam allowance beyond the sew line. Pin in place so that the bias is stable.

7.      Sew on the sew line. Since you are starting on the small dog-ear triangle of corner triangle fabric, the sewing machine will not pull your project into the throat plate.

8.      Press the corner triangle into the corner.

9.      Trim off the excess corner triangle to the intended size of the base.

10.  Fold the corner triangle back and trim the base’s replaced corner to the seam allowance.

11.  You can now proceed with other corners, if called for, at step 5 or 6.

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