A net laying ship, also known as a net layer, net tender, gate ship or boom defence vessel was a type of small auxiliary ship. A net layer's primary function was to lay and maintain steel anti-torpedo or anti-submarine nets. Nets could be laid around an individual ship at anchor, or around harbors or other anchorages. Net laying was potentially dangerous work, and net laying seamen were experts at dealing with blocks, tackles, knots and splicing. As World War II progressed, net layers were pressed into a variety of additional roles including salvage, troop and cargo transport, buoy maintenance, and service as tugboats.