A certificate assigned by the flag state or classification society specifying the minimum freeboard and maximum loading depth for each zone.
In practice
For a chief officer responsible for cargo planning, the load line is the absolute legal limit of loading. The freeboard assigned by the Convention — the distance from the load waterline to the freeboard deck — provides the reserve buoyancy that keeps the ship safe in heavy weather. Loading beyond the assigned load line is a serious criminal offence in most flag states and renders the ship unseaworthy at law. Insurance may be voided if the vessel sails beyond its assigned marks.
Regulatory detail & full definition
The International Load Line Certificate, issued under the International Convention on Load Lines 1966 as amended, assigns the ship's load lines — the marks on the hull indicating the maximum depth to which the vessel may be loaded in various conditions of voyage area and season. The Plimsoll mark and its associated lines (S, T, F, TF, W, WNA) are the physical expression of the Convention's requirements, which link loading depth to the ship's stability, buoyancy reserve, and hull strength.
For a chief officer responsible for cargo planning, the load line is the absolute legal limit of loading. The freeboard assigned by the Convention — the distance from the load waterline to the freeboard deck — provides the reserve buoyancy that keeps the ship safe in heavy weather. Loading beyond the assigned load line is a serious criminal offence in most flag states and renders the ship unseaworthy at law. Insurance may be voided if the vessel sails beyond its assigned marks.
The Load Line Certificate is one of the statutory certificates inspected by port state control. Inspectors will check that the hull markings are legible, correctly positioned, and match the certificate. They will also check the departure draught against the permitted load line for the zone and season in which the voyage begins. Officers must understand which load line zone the vessel is in throughout the voyage and ensure that loading is planned accordingly.