Because its designed for straight-stitching, Patchwork Foot #37 is ideal for sewing 1/4 or 1/8 (approx. 3 or 6 mm) seam allowances. In addition, Patchwork Foot #37 features three evenly spaced markings (1/4 apart) on its side that make the square insertion of pieces in patchworking easier. A narrow groove under the flat sole serves as a thread channel for smoother piecing..