A simple machine is a device that uses a single applied force to do work against a single load force. The two most common examples of simple machines are the LEVER and the SCREW. A LEVER is a rigid bar that pivots around a fixed point, called a fulcrum, and is used to move or lift objects. A SCREW is a cylindrical rod with a helical groove cut into its surface, which is used to hold objects together or to adjust their position.