The Add-A-Quarter ruler with its specially designed lip automatically adds the customary 1/4" seam allowance to any angle and provides a straight edge for your rotary cutter. Wonderful to use with rotary cutters and templates. It simplifies foundation piecing as you can use the tapered edge to fold back foundation papers, and works great to trim off extra fabric. Recommended by Judy Niemeyer in her foundation paper-piecing courses. Add-A-Quarter Plus 12" ruler, by CM Designs, Inc.