A lever is a basic machine made out of a stick, a beam, or a plane and a pivot point. When a force is applied to one point of the plane, the load present at another point of the plane moves. The weight is moved by passing through the fulcrum. As a result, in a basic lever machine, the fulcrum serves as a balancing point. In a machine called a "lever machine," there are two balancing points: one on top of the other one. They are called "equal" levers because they function equally well as a support for the weight being lifted. An example of such a machine is the hand-operated crane. Here's how it works: Two arms with hooks at the end of them stand up from the base. You lift something that is heavy enough, and you will be able to move both objects together. After lifting one object, you let go of it first and then lift the other one. As you can see, this is easier than trying to keep track of which object is which while you're lifting them individually! The first lever machines were built around 1770 and were used mainly for grinding lenses into shape. They were called "levelers" because they allowed one to level off an uneven surface without having to use a hammer. The loads could be quite large, so strong construction materials were needed. These days, their designs are used for many different applications where a stable platform is required.