Sheave Sheave A sheave () is a pulley with a grooved wheel for holding a belt, wire rope, or rope. The grooved wheel spins on an axle or bearing inside the frame of the block. This allows the wire or rope to move freely minimizing friction and wear on the cable. Sheaves can be used to redirect a cable or rope, lift loads, and transmit power. The words "sheave" and "pulley" are sometimes used interchangeably. A sheave can also refer to a pulley which has an adjustable operating diameter for use with a mechanical belt. This is accomplished by constructing the
Block and tackle blocks. Frictional losses also mean there is a practical point at which the benefit of adding a further sheave is offset by the incremental increase in friction which would require additional force to be applied in order to lift the load. Too much friction may result in the tackle not allowing the load to be released easily, or by the reduction in force needed to move the load being judged insufficient because undue friction has to be overcome as well. A block which is open or can be opened to engage with a bight, without the necessity to thread the