Means of closing openings in watertight bulkheads and operating sliding watertight doors
21.—(1) Every door fitted to an opening in a watertight bulkhead shall comply with the specifications set out in either Section 3 or 4 of Schedule 4 in Merchant Shipping Notice MSN 1698 (M), as appropriate.
(2) In ships constructed before 1st February 1992, doors not complying with Section 3 of Schedule 4 of Merchant Shipping Notice MSN 1698 (M) shall be closed before each voyage commences, and shall be kept closed during navigation; the time of opening such doors in port and of closing them before the ship leaves port shall be entered in the log-book.