This is a very useful tool for accurately mitering corners. Unlike all other corner jigs, this one is infinitely adjustable between 20-200 point board thickness for perfection obsessed binders. Great for one-off binding and essential for high end production work. This jig allows butt joining of cloth, paper, vellum or leather. Perfect corners every time. Instructions for use included. Bronze and Delrin. The Delrin is dimensionally stable and it is easy to clean adhesives off. 5" cutting edge.