The Add-A-Quarter™ ruler with its specially designed lip automatically adds the customary ¼-inch seam allowance to any angles and provides a straight edge for your rotary cutter. This handy little ruler helps make many tasks easier: Use it with templates: Combines the speed of rotary cutting with the accuracy of using templates. Prevents template shaving. Use it when foundation piecing: Works great to trim off excess fabric. Provides straight edge for placement of next fabric piece. The Add-A-Quarter™ ruler measures 1" x 6" and comes with complete directions for use.