Boom

From WikiPOBia

A spar running along the foot of a fore-and-aft sail. For larger sails like the spanker or driver of a ship, the boom may swing with the sail. The headsails, particularly the jibs, are only connected to their respective booms at the tack, and the jibbooms do not move with the sail. Such sails are said to be "loose-footed", while sails which are fast to the boom through their length are called "club-footed".