Block (sailing) Block (sailing) In sailing, a block is a single or multiple pulley. One or a number of "sheaves" are enclosed in an assembly between "cheeks" or "chocks". In use, a block is fixed to the end of a line, to a spar, or to a surface. A line (rope) is "reeved" through the sheaves, and maybe through one or more matching blocks at some far end, to make up a tackle. The "purchase" of a tackle refers to its mechanical advantage. In general the more sheaves in the blocks that make up a tackle, the higher its mechanical advantage. The
Lifting bag a hazardous operation with high risk of entanglement in an uncontrolled lift or sinking. If a single bag is insufficient, multiple bags may be used, and should be distributed to suit the load. There are also lifting bags used on land as short lift jacks for lifting cars or heavy loads or lifting bags which are used in machines as a type of pneumatic actuator which provides load over a large area. These lifting bags of the AS/CR type are for example used in the brake mechanism of rollercoasters. The volume of the bag determines its lifting capacity: each litre