These screws are used to cut or form a mating thread when driven into preformed holes. They permit rapid installation, since nuts are not used and access is required from only one side of the joint. The mating thread produced by the tapping screw fits the screw threads closely, and no clearance is necessary. Tapping screws are used in steel, aluminum, die castings, cast iron, forgings, plastics, asbestos, and resin-impregnated plywood.