a ship is constructed of a skeleton , including a hull , horizontal decks , and vertical support posts , all permanently joined together . at least some of the interior walls are made of a composite material of reinforcement embedded in a plastic matrix . these non - structural interior walls are semi - permanently attached to the skeleton with attachments , so that they may be readily rearranged to reconfigure the interior of the ship . the majority of the apparatus and infrastructure of the ship is affixed to the skeleton but not to the non - structural walls .