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 just
thread, A screw 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.