The Infamous HST: Half-Square Triangle Tutorial

HST Tutorial Cover e

There are a few basics I thought I would write into tutorials for the Sisters' Ten Block of the Month Club.  This way I can let you know my method, and refer to the tutorial, instead of having to give the same directions over and over again.  Today we start off with Half-Square Triangles.

HST 1 tutorial

Cut 2 squares the same size.  One from Fabric A and one from Fabric B.

Draw a diagonal line on the wrong side of the Fabric A square.

HST 1.  draw diagonal e

Layer the Fabric A square atop the Fabric B square with right sides together.  Sew pairs together, stitching 1/4" on each side of the drawn line.

HST 2.  sew on either side of diagonal e

Cut the pair apart along the drawn line to make two half-square triangle (HST) units. 

HST 3. Cut on drawn line e

Press open the half-square triangle blocks, pressing seams toward the dark fabric, Fabric B.

HST 4. Open, press seams to dark e

To square up the blocks, I like to mark off the unfinished size I am going to trim the HSTs down to.  I lay post-its on the ruler so I can see the unfinished size without getting confused.  (In this example, I have gridded off a 2 7/8" x 2 7/8" square.

HST 5. mark required unfinished size e

Lay the diagonal of the ruler on top of the diagonal of the HST.  Make sure to center the marked-off section of the ruler over the block so there is a small amount of fabric to trim on all sides.

HST 6. Lay fabric diagonal along ruler grid diagonal e

Use your rotary cutter to trim the excess on all sides.

HST 7.  Trim away excess e

All finished!

HST 8.  Finish e