The actual wheel of a pulley Block. Special types of

sheave are made for rope, wire and chain. The larger the diameter of the sheave the more easily the cable

will run, and there is a definite minimum size for each size of cable. The size of block is proportioned to size of

rope, with sheave diameter, Score and Swallow all in harmony. The noticeably

large sheaves used with small ropes in the multi-part mainsheet tackles on some

racing dinghies are made that way for easier Rendering – in other words for

maximum mechanical efficiency.