Boom

A spar attached to or associated with a mast that controls the foot and position of a sail.

On a conventional mainsail the boom extends aft from the mast, supports or tensions the sail’s foot and transfers loads from the mainsheet, vang or kicking strap, outhaul and reefing systems. It pivots across the vessel as the sail is trimmed or changes side.

Not every sail or rig uses a boom, and a boom does not by itself prevent luffing or create the designed sail shape. Because it can sweep the cockpit or deck rapidly during a tack, gybe or loss of control, people and equipment should be kept clear of its travel and associated loaded lines.