Half Square Triangle

How to make half square triangles

Here are some simple half square triangle instructions. A half-square triangle is a name for a very simple quilt block or unit of a block. When you see it, you might be tempted to call it a two-triangle square or a square made up of two triangles. But most quilters know it by it’s funny name, a half-square triangle. It looks like a square with one diagonal line.

It is simple to make in theory, but some quilter’s find it hard to execute. The method used to make a half-square triangle is simple, but perfection in all steps is, as always, the key to excellence.

There are several ways to construct the block. One way is to make it with two squares.

Step 1 is to cut two squares, from two different fabrics.

Step 2 is to sew two diagonal lines, one half inch apart, centered from one corner to an opposite corner. The trick is to sew those two lines exactly 1/4″ way from both sides of the center diagonal.

Step 3 is to cut between the two rows of stitching and press each seam allowance to one side.

All this is easy to do, but hard to get right. Aside from human error, like cutting inaccurately or stitching with a too large or too small seam allowance, fabric has a life of its own. It tends to shrink up if too much heat from an overly hot iron is used, thereby producing a skewed block. Many quilters insure an accurate block by making their half-square triangle a little bigger than they need, and then trimming it down to the correct size.

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