THE WATERWAYS HERITAGE SPOTTER: HOOKS AND PULLEYS

摘要

Look at the top of the coping stones on the offside (non-towpath side) wing walls at the head or tail of many of the locks on the Worcester & Birmingham Canal, and sticking out of the top of one of the stones you may well see a small, curved iron spike. This, to give it its proper name, is a blocking hook - and its function was to help make work easier for boat horses, in the days before powered craft. As anyone who's had to bowhaul a boat will appreciate, the hardest part for a horse was getting a fully loaded boat started from the constricted channel of a lock chamber. Once the boat was moving, keeping it going was relatively light work and the horse could keep it up all day. The idea of the blocking hooks was to make the horse's job easier by providing a two-to-one mechanical advantage, in the same way that pulleys are used to make lifting heavy loads easier - in fact the word 'blocking' refers to the (often maritime) use of 'block' to mean a pulley.