The Wedge is a device that tapers to a thin edge, usually made
of metal or wood, and used for splitting, lifting, or tightening,
such as to secure a hammer head onto its handle.
The wedge is considered one of the six simple machines. Wedges
have been used since prehistoric times to split logs and rocks; for
rocks, wooden wedges, caused to swell by wetting, have been used.
In terms of its mechanical function, the screw may be thought of as
a wedge wrapped around a cylinder.