A lever is a simple mechanism that uses a bar to pivot ... Linkages are found in many different machines, including folding chairs, windscreen wipers and the arm of a digger.

A simple lever could be a solid beam laid across a pivot. As effort is applied to rotate one end about the pivot. The opposite end is also rotated about the pivot in the same direction.

Simple machines can be regarded as the elementary "building blocks" of which all more complicated machines (sometimes called "compound machines") are composed. For example, wheels, levers, and pulleys ...