On a square rigged ship, the spanker is a gaff-rigged fore-and-aft sail set from and aft of the aftmost mast. Spankers are also called driver, jigger, and a pusher sail. On a schooner of four or more masts, the spanker is the sail on the mast nearest the stern. The spanker is a small sail, but as it is so far aft of the balance point of the hull, it has strong leverage: when sheeted in, the spanker is important in driving the boat to a new tack. References Sailing rigs and rigging fi:Kahvelipurje sv:Gaffelsegel