Gaff rig

Gaff rig is a sailing rig (configuration of sails) in which a sail is a four-cornered fore-and-aft rigged item controlled at its peak and, usually, its entire head by a spar (pole) called the gaff. The gaff enables a fore and aft sail to be four sided, rather than triangular, and as much as doubles the sail area that can be carried by that mast and boom, if a boom is used in the particular rig.