Abstract: A sail boom clamp has two opposing jaws (22) and (23) which fit around a mast (2) in use to hold a sail boom in position. The effective separation of the jaws (22) and (23) can be altered by cooperation between a foot 40 on an underside of the jaw (23) and steps in an arcuate wedge (41). The wedge is moved to present different of the steps to the press against the foot (40) in use to hold the jaw in different positions relative to a body (20). The jaws are closed and held closed by an over-center clamping arrangement consisting of a handle (26) and a wire loop (24).