Strong transverse pieces of timber stretching across the ship from one side to the other, to support the decks and retain the sides at their proper distance, with which they are firmly connected by means of strong knees, and sometimes of standards. They are sustained at each end by thick stringers on the ship's side, called shelf-pieces, upon which they rest. The main-beam is next abaft the main-mast, which is stepped between two beams with transverse supports termed partners; the foremost of these is generally termed the main-beam, or the after-beam of the main-hatchway. The greatest beam of all is called the midship-beam.