Omnigrip's Non-Slip Square Quilter's Ruler is made especially for quilting, sewing and crafting projects to cut strips and square up finished quilt blocks. There's a diagonal line for triangle cuts and the ruler can be used with rotary cutters or straight edge blades.Details:Clear with neon and black markings20.5" x 20.5"Extra 1/2" on two sides for seam allowanceEdge markings for accurate measuringLaser-cut edgesLeft- and right-hand numbering and angle systemDouble-sight lines visible on light and dark fabricsNon-slipAcrylicFor use with rotary cutter or straight-edge blade