20 Ways to Make HSTs – Half Square Triangle Quilt Blocks – Traditional Method

The Half Square Triangle Block is one of the basic building blocks used in making quilts. Half square triangle units (HSTs) are squares made up of two triangles. Each triangle occupies half of the square’s space. As you might expect, there are many, many different methods to make those blocks. This tutorial shows you 20 of the most common methods.

First, a glossary.

A finished HST is the size that it is in a quilt. It’s dressed and ready to go to the ball. An unfinished HST is in raw, unclothed form. It will be 1/2″ larger than a finished HST because the size includes a 1/4″ seam allowance.

Making HSTs using Traditional Methods

The Traditional Method of making Half Square Triangle Blocks (HSTs) is to place two identical squares right sides together. These squares should be 7/8″ larger than the finished size of the final HST. Draw a diagonal line on the back of one square. Sew 1/4″ on both sides of the line. Cut on the line and press to the dark.

You will have made two identical Half Square Triangle (HST) blocks. My personal preference is to cut squares 1″ larger than the finished size of the final HST and square it up to the correct size after pressing.

Marking the Diagonal Line with a Ruler

To use a QRQQ ruler, lay it on the diagonal of the back of the lighter square. Match it to the same size darker square, right sides together. Using a mechanical pencil, draw a dotted line through the center of the ruler. If you like, you can also draw a line along both sides of the ruler. That will be your sewing line which is 1/4″ from both sides of the dotted line. Cut on the dotted line.

Here is a video that I made back in 2009: http://youtu.be/OQq-5p8RCS8. I am using a Rotating Cutting Mat in that video, and a Fussy Cut Ruler by Quilt in a Day. I bought the complete set because I find myself using them constantly. That diagonal line and the marked quarter-inch seam allowance help tremendously with making accurate blocks.

Marking the Diagonal Line without a Ruler

Triangle Tiger Tape uses the same method to make HSTs, Flying Geese, and Snowball blocks without pencil lines. Align the arrow points of the tape, and sew along the outside edges. Remove the tape (which is reusable) and cut between the stitching.

This is an old picture because they don’t seem to make this product any more. However, the 1/4″ Tiger Tape itself is still made. It just has straight lines on it now, rather than angled lines. You can use it the same way just by placing it along the diagonal line of your block, then sewing on either side of the tape.

Using Repositionable Vinyl Ruler Stops

In the video below, Marci Baker is showing how to accurately cut squares from strips using Cutting Edge Ruler Stops. This product is a little hard to find, but I have substituted both Omnigrid Glow-Line Tape and Sewing Edge Reusable Vinyl Stops for your machine and they work just as well. She does not mark her diagonal line. She presses the square along the diagonal and uses that as her guide. This method depends on her having an accurate 1/4″ seam allowance, which she ensures by using the Sewing Edge Reusable Vinyl Stops.

Squaring up the Block

You can place a square ruler so the diagonal line is directly over the seam and just cut two sides. Quilt-in-a-Day has a Square Up Ruler that uses this method.

Or you can press open the block (pressing to the dark) and square it up using a ruler the same size as the block you are making. A fussy-cut ruler with lines on both diagonals will be very helpful with this.

Here are two rulers from Creative Grid.

If you don’t see the size you need, you can always make your own using Template Plastic. If you need something urgently, try printing out this graph paper and glueing it to a light cardboard, like the back of a cereal box.