The most versatile tool to move loads. The principle is used in many other tools here described.

In engineering, levers are described by their three components:

•     Load arm: Lever arm on the side of the load to be moved.
•     Force arm: lever arm on the side of the moving force
•     Pivot point: point around which the lever can rotate.

Using these terms, the law of leverage reads: "force times force arm equals load times load arm".