Rope drive tensioned by an idler pulley, but this system was not used in the UK and each loop was tensioned between its two pulleys by one of them being movable. Rope drives were also cheaper than belts, around a quarter of the price. The rope drives were placed in a large diagonal shaft at the side of the building, usually windowless and distinctively visible from outside the building. Rope drives required a larger such shaft than comparable belt or shaft drives. As the open shaft represented a channel for transmitting fires, unlike the narrow holes of a shaft drive, it needed
Block (sailing) matter is slightly complicated by the fact that every tackle has a "working end" where the final run of rope leaves the last sheave. More mechanical advantage can be obtained if this end is attached to the moving load rather than the fixed end of the tackle. There are various types of blocks that are used in sailing. Some blocks are used to increase mechanical advantage and others are used simply to change the direction of a line. A "ratchet block" turns freely when a line is pulled in one direction but does not turn the other direction, although the