The "Mary Rose" was built according to the carrack-style with high "castles" in the bow and stern with a low waist of open decking in the middle. The shape of the hull has a so-called tumblehome form and reflected the use of the ship as a platform for heavy guns. Above the waterline, the hull gradually narrows to compensate for the weight of the guns and to make boarding more difficult. Since only part of the hull has survived, it is not possible to determine many of the basic dimensions with any great accuracy. The moulded breadth, the widest point of the ship roughly above the waterline, was about 12 metres (39 ft) and the keel about 32 metres (105 ft), although the ship's overall length is uncertain.