Most bulkheads provide four important functions within the ship. First, they act as stiffeners for the entire hull structure; secondly, they distribute the vertical forces of weight and buoyancy through the hull's structure; thirdly, and most obviously, they serve to separate the ship's activities and functions; and, finally, they provide watertight subdivision. Some bulkheads, such as the main transverse bulkheads, are constructed to withstand severe hydrostatic pressure and the fluctuating stresses that might be imposed through flooding in free communication with the sea. The first function(stiffening the hull's structure) is accomplished primarily by the main transverse bulkheads that extend continuously through the watertight volume of the ship from keel to main deck. Figure 11-28 shows a main transverse bulkhead at the forward end of the machinery spaces in a destroyer. These bulkheads resist the longitudinal twists and transverse stresses in the structure since they are stiffened both vertically and horizontally by stiffeners supported at the bottom, sides, and deck by brackets.