The ship’s internal and external frame is constructed of large pieces of plate and then fitted with decks and bulkheads. Shipfitter apprentices contribute to all structural phases of the ship’s hull construction, including fabrication, assembly, and alignment of the ships structures. They position and fit steel together, so that the pieces can be permanently welded in place. Apprentices learn to tack weld to prevent their assemblies from moving. They also install other structural components, such as hatches, doors and foundations to complete the steel work of the ship and gain experience in submarine and aircraft carrier construction and aircraft carrier overhaul.