Omnigrip Quilting Ruler - 12 1/2" SquareThe Omnigrip 12 1 2"" square has a diagonal line for triangle cuts; the ruler has extra 1 2"" on two sides for seam allowance. Ideal for secondary cutting of strips, and to square up finished quilt blocks Heavy duty durable acrylic material Diagonal line for triangle cuts; Left and right hand numbering and angle system Patented non slip backing to hold ruler in place during cutting Edge markings for accurate measuring and laser cut edges for smooth,