This is a great tool from Clover, it is part of their Nancy Zieman range.  Effortlessly cut, mark and stitch a triangle without cutting a trianle or guessing at sizes.  The No-Hassle triangle gauge cab be used to make five block sizes from 2 1/2 inch to 6 1/2 inch for both 1/2 and 1/4 square triangles. The push button sliding gauge locks for accuracy