Omnigrip by Omnigrid features basic size rulers with a fabulous feature: non-slip backs! Omnigrip also features a left- and right-handed numbering and angle system and transparent, neon green double-sight lines. Measurements are printed on the ruler for the squares needed to cut all side corner triangles. The "square master," this ruler can be used to square up any finished block up to 12-1/2". The 1/2" seam allowance is included on 2 sides, making it perfect for cutting background blocks. Also convenient for cutting larger, custom size squares, rectangles and wide borders.