The number markers on each side of a ship at the bow, stern, and amidships, to indicate the distance from the lower edge of the number to the bottom of the keel or other fixed reference point.
In most cases draught marks cannot be located exactly on fore perpendicular due to shape of the bow. Situation at the stern is even worse and often a lower part of draught marks is located on the rudder and the upper part on the transom. For these reasons draught values as measured on draught marks cannot be used directly to evaluate hydrostatic parameters and must be first recalculated. A procedure how to calculate mean theoretical draught on the base of draughts as measured on draught marks are described on the drawing of Draught Marks.