What is a wedge?

A wedge is a simple machine. It consists of a rigid object with narrow end and a wider end. It is used to change the magnitude and/or direction of an applied force.
Typically forces applied to the blunt end (the top of the wedge in the figure above) are converted into forces acting perpendicular to the long faces of the wedge.
Wedges are used to hold objects in place (a doorstop is an example of this), to separate surfaces (all knives, axes, and swords are wedges), or to lift objects. Long thin wedges used in carpentry to adjust the alignment of parts prior to finishing are called shims.