This is one of my favorite tools that makes it so easy to create 1/2 square and 1/4 square triangles. 

Create triangle blocks effortlessly without ever having to cut triangle or guess sizes.

Create 2-1/2" (64mm), 3-1/2" (89mm), 4-1/2" (114mm), 5-1/2" (140mm) and 6-1/2" (165mm). 

Use the left side of the gauge for 1/2 (half)-square triangles and the right side for 1/4-square triangles. The gauge locks for even better accuracy. 

Check out our full blog post on making 1/2 (half) square triangles here. https://sewingbysarah.com/blogs/tutorials/how-to-make-1-2-square-and-1-4-square-triangles-using-our-triangle-gauge

Here's a quick video overview of the process: