Alvin 42" Paral-Liner parallel drafting straightedge is constructed of rigid black phenolic plastic with satin finish. Features integral comfort grip bar to control straightedge movement. Mobile straightedge affords frictionless operation through the floating action of the nylon rollers mounted on the blade. The rollers retract at a touch, securing the blade for accurate drawing. Clear acrylic plastic edges are elevated to prevent ink smears and steel ball-bearing pulleys provide smooth movement. Includes all mounting hardware and installation instructions.