Boatswain's Mates (BM) train, direct, and supervise personnel in ship's maintenance duties in all activities relating to marlinespike, deck, boat seamanship, painting, upkeep of ship's external structure, rigging, deck equipment, and boats; take charge of working parties; perform seamanship tasks; act as petty officer-in-charge of picketboats, selfpropelled barges, tugs, and other yard and district craft; maintain discipline as master-atarms and police petty officers; serve in, or take charge of, guncrews or damage control parties; and operate and maintain equipment used in loading and unloading cargo, ammunition, fuel, and general stores.