A line painted amidships that fixes how deep a ship may sit: the load line convention and its three annexes

Background

How deeply a ship can be loaded is set by its freeboard, and the limits are drawn on the hull as load lines. The first convention of this kind was adopted in 1930 and rested on the principle of reserve buoyancy. The convention of 1966 that was drawn up at IMO works out freeboard from subdivision and damage stability calculations. Its rules take account of the hazards of different zones and different seasons. All assigned load lines are painted amidships on both sides of a ship, beside the deck line. A ship carrying timber on deck is given a smaller freeboard, because the deck cargo itself shields it from waves. The convention carries three annexes, and the first of them is divided into four chapters. Zones, areas and seasonal periods sit in the second annex, while the third holds the certificates.