Gaff rig[1] is a sailing rig (configuration of sails, mast and stays) in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the gaff. Because of the size and shape of the sail, a gaff rig will have running backstays rather than permanent backstays.
The gaff enables a fore-and-aft sail to be four sided, rather than triangular. A gaff rig typically carries 25 percent more sail than an equivalent Bermuda rig for a given hull design.[2]
A sail hoisted from a gaff is called a gaff-rigged (or, less commonly, gaff rigged or gaffrigged) sail.[3]