The structure of the hull varies depending on the vessel type. In a typical modern steel ship, the structure consists of watertight and non-tight decks, major transverse and watertight (and also sometimes non-tight or longitudinal) members called bulkheads, intermediate members such as girders, stringers and webs, and minor members called ordinary transverse frames, frames, or longitudinals, depending on the structural arrangement. The uppermost continuous deck may be called the "upper deck", "weather deck", "spar deck", "main deck", or simply "deck". The particular name given depends on the context—the type of ship or boat, the arrangement, or even where it sails. Not all hulls are decked (for instance a dinghy).
In a typical wooden sailboat, the hull is constructed of wooden planking, supported by transverse frames (often referred to as ribs) and bulkheads, which are further tied together by longitudinal stringers or ceiling. Often but not always there is a centerline longitudinal member called a keel. In fiberglass or composite hulls, the structure may resemble wooden or steel vessels to some extent, or be of a monocoque arrangement. In many cases, composite hulls are built by sandwiching thin fiber-reinforced skins over a lightweight but reasonably rigid core of foam, balsa wood, impregnated paper honeycomb or other material.
Carvel built or carvel planking is a method of boat building where hull planks are fastened edge to edge, gaining support from the frame and forming a smooth surface.
It contrasts with clinker built hulls, where plank edges overlap. Carvel construction gives a stronger hull capable of taking a variety of full-rigged sail plans, albeit one of greater weight. On the upside, Carvel built construction enables greater length and breadth of hull as well as superior sail rigs because of its strong framing, and is one of the most critical development that enabled the centuries long dominance of of Western European seapowers in the Age of Sail and beyond.
Carvel developed through transition from the age-old Mediterranean mortise and tenon joint method to the skeleton-first hull building technique which gradually emerged in the medieval period.