A screw, or bolt, is a type of fastener,
typically made of metal, and characterized by a helical ridge, known as a male thread(external thread) or
wrapped around a cylinder. It is an inclined plane wrapped around a nail. Some
screw threads are designed to mate with a complementary thread, known as a female thread (internal thread), often in the form
of a nut or an object that has the internal
thread formed into it. Other screw threads are designed to cut a helical groove
in a softer material as the screw is inserted. The most common uses of screws
are to hold objects together and to position objects.