Plimsoll Lines
Search the hull of a merchant ship and you will find a curious ladder of lines punched or welded to the hull and picked out in paint. It will consist of a vertical line with horizontal steps to left and right labelled with letters, such as TF and F to one side and W, S, T and sometimes WNA on the other. Close to this is a circle with a horizontal line through it, like the planet Saturn with its rings, and some more letters. These will be the initials of one of twelve internat
