the running rigging of a sailing vessel controls the sails. the running rigging is usually made up of various kinds of rope (ropes are also called lines). it uses blocks and sheaves to adjust the length of the ropes. a block is a kind of pulley. a sheave is the grooved wheel inside the block. larger sailing boats and ships use winches. the adjustability of the running rigging allows the boat to perform various maneuvers such as tacking and jibing. common to all sailboats are the outhaul and the downhaul. the outhaul pulls the sail to the free end of the boom. the downhaul keeps the boom from rising on the mast.