By Laura Loewen

Quarter-square triangles (QST) are easy to assemble. These units are commonly used to make a double pinwheel block. They are sometimes referred to as 3-patch QST, or 3-square QST. They differ from an hourglass, which can also be referred to as a quarter-square triangle block.

You start with 3 cut squares and end up with two QST units. Begin by cutting two squares 1.5” larger than your finished QST, these pieces will be the quarter triangles. Cut one square 1” larger than your finished QST, this is the half triangle. Our example shows a 3” finished QST. So we use two squares cut at 4.5” and one square cut at 4”.

Step 1

Cut (2) squares 1.5” larger than your finished QST for the quarter triangle pieces. Cut (1) square 1” larger than your finished QST for the half triangle pieces.

Step 2

Assemble HST units from your larger squares. See our paired HST tutorial for detailed instructions. Don’t forget to trim. HST units will be the same unfinished size as your third square.

Step 3

Discard, or set aside, one HST unit. Place remaining HST unit and cut third square right sides together.

Step 4

Draw diagonal line, perpendicular to HST seam, from corner to corner.

Step 5

Sew ¼” on either side of drawn line.

Step 6

Cut on drawn line. (picture shows one unit flipped over to illustrate the new seams are perpendicular to the original HST seam)

Step 7

Press open and trim ½” larger than finished QST. Take care to line up all diagonals at corners.