Alvin® Paral-Liner® 60" Mobile Parallel Straightedge This 60" straight edge features rigid phenolic construction with a black satin finish. The larger size ensures that it will be compatible with most blueprints and large drawings. Nylon rollers on the straight edge ensure that it can glide across fresh pencil and ink drawings without smudging or smearing. As an added bonus, these rollers are retractable. The blade can be instantly secured. The edges are made of elevated Plexiglass so that you can be sure your drawings are accurate. The straight edge comes with all needed mounting hardware and installation instructions. Installation takes minutes, and can be done on your own with simple tools.