31.—(1) Watertight or weathertight doors above the margin line (except doors fitted in collision bulkheads to which regulation 28 applies) which are fitted in bulkheads which are required to be watertight or weathertight as the case may be and which separate or form the boundary of cargo spaces shall be closed and locked before the ship leaves its berth and be kept closed and locked until the ship has been secured at its next berth.
(2) Watertight and weathertight doors above the margin line fitted in the shell or in bulkheads which are required to be watertight or weathertight, other than those doors described in regulations 28(1) and 31(1), shall be kept closed whilst the ship is on any voyage except when opened on the express authority of the master.
(3) Any watertight or weathertight door which may be opened in accordance with the exception to paragraph (2) shall be kept clear of obstructions which might prevent its rapid closure.