Cutting a single helical groove into a screw-stock cylinder yields what is referred to as a single-thread screw. Similarly, one may construct a double-thread screw provided that the helix angle is the same, and a second thread is cut in the space between the grooves of the first. For certain applications, triple and quadruple threads are in use. The helix may be cut either right hand or left hand. In screws especially, the helix angle is essential for calculating torque in power screw applications.