Parallel slots for precision markings from 1/4-inch to 3-3/8-inch.See Thru Ruler; 4-inch by 15-inch. Clear plastic slotted for making parallel markings. Use for measuring and marking exact locations of buttons, buttonholes, pockets, etc. Simplify patten alterations. Measure staight of grain from fabric selvages. Guide tracing wheel and pencil markings. Measure and mard spacing for pleats and tucks, bias strips,guide lines for decorative stitching. Draw guide lines fro undercollar padstitching.