Square Ruler, 12-1/2" x 12-1/2"The Omnigrid 12 1 2" x 12 1 2" ruler features an extra 1 2" width for seam allowances; it is used to cut, square and trim blocks sized 12 1 2" and under when quilting. In general, Omnigrid square rulers are used for secondary cutting of strips, and to square up finished quilt blocks Use with a rotary cutter or a straight edge blade The 12 1 2"" x 12 1 2"" ruler has the following standard Omnigrid features: Diagonal angle line Edge markings for