Omnigrid's Neon Square No-Slip Ruler is used to cut strips and square up finished quilt blocks. You'll find Omnigrid rulers ranging from 3-1/2" square to 20-1/2" square. Each ruler has a unique non-slip backing that eliminates slipping when measuring and cutting, as well as 45 ° diagonal lines for triangle cuts, markings for half-squares, and quarter-square triangles. They are made of heavy-duty, durable acrylic material and feature a left- and right-hand numbering and angle system. There are patented neon green double-sight lines that seem to glow on fabric, making measuring and cutting a breeze.