Oh what fun you are going to have with this no-slip ruler. A fast, fun way to make half square triangles. Uses popular 10 and 5 squares of fabric to give you quick and accurate half-square triangles in 4 1/2 (4 finished size) and 2 (1 1/2 finished size). Also a great tool for squaring up other blocks because of the easy to read lines and NO SLIP SURFACE. You will find this is a handy ruler to have around. I have been using it for squaring up my blocks on my new paper piecing project and I love it.