Alvin® Paral-Liner® 30" Mobile Parallel Straightedge Draw clean, smooth lines with precision with this excellent straightedge tool for professionals and amateurs alike. The soft grip and spinning, retractable nylon rollers glide the straight edge upon the blade; you will always hit your target! Constructed with a phenol-condensed resin and an aluminum surface, the Alvin Parallel Straight Edge 30In will not rust from fingertip moisture. The raised acrylic edges prevent ink smears and a special feature of this handy strait edge -- the recessed ledge -- is great for storing drawing pencils. The Alvin Parallel Straight Edge 30In is the tool to use for drafting square lines, triangles and rectangles. Complete instructions and installation hardware comes in the package … you can attach the Alvin Parallel Straight Edge 30In onto a solid wooden or similar drafting table (glass is NOT recommended). The Alvin Parallel Straight Edge 30In holds a steady guide for all of your drafting needs.