Cal-Royal continuous geared hinges are designed to provide superior performance you can rely on in high-traffic areas because instead of using a pin as in conventional hinges, we use a geared rotating joint. Weight is distributed evenly along the full length of the frame, thus minimizing wear on the hinge. Approved for use on swing type doors of hollow metal, tinclad, sheet-metal and steel covered composite type rated up to and including 3 hours. Wood composite doors rated up to and including 1 1/2 hours.