Lug sail

The lug sail, or lugsail, is a fore-and-aft, four-cornered sail that is suspended from a spar, called a yard. When raised, the sail area overlaps the mast. For "standing lug" rigs, the sail may remain on the same side of the mast on both the port and starboard tacks. For "dipping lug" rigs, the sail is lowered partially or totally to be brought around to the leeward side of the mast in order to optimize the efficiency of the sail on both tacks.

The lug sail is evolved from the square sail to improve how close the vessel can sail into the wind. Square sails, on the other hand, are symmetrically mounted in front of the mast and are manually angled to catch the wind on opposite tacks. Since it is difficult to orient square sails fore and aft or to tension their leading edges (luffs), they are not as efficient upwind, compared with lug sails. The lug rig differs from the gaff rig, also fore-and-aft, whose sail is instead attached at the luff to the mast and is suspended from a spar (gaff), which is attached to, and raised at an angle from, the mast.^[1]