NEW Diagonal Set Triangle Rulers - Full Triangle

New Diagonal Set Triangle Rulers

Product No. 8105
for 2-1/2" to 10" block
Order this ruler


Product No. 8104
for 5" to 16" blocks
Order this ruler







Cutting Perfect Corner and Setting Triangles with Proper Grainline is Easy with These Rulers

Diagonal set quilts have two different half-square triangles: one for the corners and one for the setting triangles. Use this “no math” ruler to cut both triangles from the same-width strip of fabric.

What are corner and setting triangles? quilt definitions
a = The finished block size is calculated and includes ¼″ seam allowances.

b = The corner triangles are cut with the legs on straight grain.

c = The setting triangles that fill in the ends of the diagonal rows are cut with the hypotenuse on the straight grain.

Cutting the Strips for Both TrianglesCutting Strips

Locate your finished block size (a) on either diagonal edge or down the center of the ruler. The arrows point to a line. Place that line on the trued-up edge of the fabric. Place a long acrylic ruler against the small tip of the Diagonal Set Triangle Ruler. Slide the triangle along the fabric edge to confirm consistent strip width, then cut the strip. Option: In the center of the ruler, the numbers 2″ to 7″ identify a ruler that can be read to determine actual strip width. Then measure and cut strips any way you like.

Cutting triangles for an 8″ block is illustrated. Corner and setting triangles are cut from the same width strips.

Cutting Strips

Corner triangles must be cut from a trued-up end of the strip.

Cutting the Corner Triangles (b)

True up one end of the strip. Position the solid line just left of the center of the tool on the cut end of the strip and the line of the finished block size at the bottom of the strip. The tip of the ruler should align with the top of the strip. Cut the diagonal edge; before moving the ruler, nip the point.

Nip the point

Reposition the ruler as needed on the cut triangle so the corners align and nip off the other two points. Nipping the points on all the setting and corner triangles allows them to line up perfectly with blocks when rows are assembled.

Cutting Corner Triangles

Cutting the Setting Triangles (c)

Assuming you have just cut a corner triangle, rotate the ruler on the same strip. Position the line identified for your finished block size on the top edge of the strip. The flat top of the ruler should just touch the bottom edge of the strip, and the angled edge of the ruler should line up with the angled edge of the strip.

Cut the diagonal to create the first setting triangle (1, below left). Reposition the ruler on the corners of the fabric triangle as before and nip off the points.

Cutting Setting Triangles

Rotate the ruler and align the block size line on the other edge of the strip and cut again (2, above right). Nip off the points.


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NOTE: Most of the instructional information and artwork shown is excerpted from my books. Like other published material, it is protected by copyright law, but you have my permission to print and download these materials for your own non-commercial use.

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