Prime-line n 7273 bi-fold door hinge, 3 in., steel, satin nickel plated, non-mortise pack of 2 these bi-fold door hinges are constructed of steel and come in a zinc plated finish. They feature a non-mortise design allowing them to be easily mounted on the door’s edges, avoiding the need to chisel and mortise for installation. For best results, use a 3/32 in. Bit to drill pilot holes prior to screwing in fasteners to avoid splitting wood. These door hinges are used on bi-fold doors by many wardrobe door manufacturers.