Pulleys make it easier to raise and lower heavy loads. We can find them all around us, on boats, bikes, flagpoles, and many more places. Pulleys are made up of an axle and a wheel with a groove around its edge. The grove keeps a rope, chain, or cable from slipping off the wheel. Pulleys come in a variety of sizes and materials and can either be fixed or moveable. When two or more pulleys work together, they're called compound pulleys. Readers will learn these facts, see examples of how they are used, learn about the pulley's inventor, and learn where pulleys can be found in their daily lives.