Four common types of simple machines are the lever, axle and wheel, inclined plane and pulley. Pulleys are often used to lift objects, such as bricks, flags and pianos.
Pulleys are often made of a wheel or disk; an axle; and a cable, rope or chain. The wheel or disk is attached to an axle, and the rope, chain or cable is looped around the disk.
A pulley moves objects by altering their direction, amount of speed of force, according to the University of Arkansas.
Pulleys are used on sewing machines, flagpoles, sailboats, clotheslines, window blinds and cranes.
A block-and-tackle is a type of pulley system that contains a row of pulleys attached to a rope structure, according to the Microsoft Encarta Encyclopedia. A chain hoist is a pulley system that is connected by a group of chains, which people use to move objects upward.
Objects similar to pulleys, which contained vines or ropes, are believed to have been used by the Mesopotamians as early as 1500 B.C. to lift water buckets, according to the Microsoft Encarta Encyclopedia. During the 12th century, people used pulleys to build cathedrals, according to the University of Nebraska-Lincoln.