The quarter-square triangle unit is constructed in a similar manner to the half-square triangle unit, only it contains a few more steps. The special math number for this unit is 1 ¼-inch. That means you will add 1 ¼-inch to the measurement of your desired finished (sewn) square.
Begin as you did for the half-square triangle. Cut your squares (or rectangles if you are making double units). Starch them according to the directions I gave in the half-square triangle tutorial.
Mark your cut squares or rectangles just as you did for the half-square triangle units.
Next, sew scant ¼-inch seam lines on both sides of your cutting line.
When you’ve completed your stitching, cut the units apart with your rotary cutter or scissors. Press them open.
Now we begin the additional steps. Take one unit and turn it to the wrong side. Place it on top of a second unit, placing the light color over the dark and the dark color over the light as pictured.
With a ruler and pencil, draw a line from corner to corner, perpendicular to the stitched seam. Gently snuggle the two opposing seams together (so that they butt up against each other) and pin in place.
Sew a scant ¼-inch seam on each side of your cutting line.
Place your ruler on the cutting line and cut your units in half.
Open and press. You should now have perfectly matched quarter-square triangle units, which are sometimes called hourglass units. Square them with your quilting ruler if necessary.
In the next tutorial, I will show you how to make perfect little four-patches. I think you’ll like my method, both for its simplicity and accuracy.