(Submitted by Marje Rhine, pattern editor for American Quilter magazine)
Some quilt patterns call for quarter-square triangles (QST), which are triangles cut from a square on both diagonals (fig. 1). These triangles are used instead of half-square triangles when the quilt designer wants the fabric's straight of grain to fall on the long edge of the triangle. This adds stability to the block.
Often the large outside setting triangles for on-point quilt layouts are QSTs (fig. 2). One square produces 4 triangles, but sometimes a pattern calls for fewer than 4 QSTs, so there may be some left over after cutting. For small triangles this is not a problem, but it can result in a waste of fabric if the original square is large, as is often the case for setting triangles. Or, there may not be enough fabric left to cut a large square for additional QSTs.
Special rulers may be purchased to help you cut these triangles one at a time. However, it is easy to do with just a large, square rotary-cutting ruler that you probably already have on hand.
First, make sure the strip or piece of fabric is at least as long and half as tall as the square size given for the QSTs. My pattern called for one 11 1/4" QST, so my fabric must measure at least 11 1/4" long x 5 5/8" tall.
Straighten the edge of the fabric.
Make small marks on the long edge of the fabric 11 1/4" apart (fig. 3).
Rotate a large square ruler so the starting point for the measurements on 2 sides of the ruler are at the top point. Place the ruler on the fabric so the edges of the ruler touch the marks on the fabric.
Maneuver the ruler so the same measurement mark is at each of the 2 marks on the fabric. In this example the marks on the fabric fall just inside the 8" lines on the 2 sides of the ruler (fig. 4). Cut out using a rotary cutter, and you'll have one 11 1/4" QST.