Winches: Old oil and grease lose viscosity and winches will slip when springs and pawls get stuck. Typical thicknesses are 6mm (1/4") and 10mm (25/64"). Aluma-Lite - Aluma-lite is a good option for large rigid signs. http://bookmarkport.com/story6268207/door-safety-or-how-safe-is-you-part-two