A sheave is a grooved wheel or pulley that is used in mechanical engineering and lifting equipment. It is a wheel with an open groove that a rope or cable fits around so it can rotate around the exterior. One end of the cable is attached to an item that needs to be moved, while the other is attached to a fixed object, like the base of a crane. The cable smoothly moves over the wheel of the sheave as it is wound up on the fixed object, lifting the other object into the air. Sheaves are also commonly known as pulleys, and when two or more pulleys are used together for extra strength, this is known as a sheave block. The terms pulley and sheave are often used interchangeably, and there is little to no difference between the two. Sheaves can be made of different materials, but they are typically made with an alloy mix of iron and steel, and some models also add carbon and silicon for extra durability.