What is lashing in shipping?

Below deck, containers stand in cell guides and need no lashing. On deck each box is locked to the one beneath it by twist-locks in the corner castings, and the lower tiers are additionally tied down with lashing rods: steel bars hooked into a corner casting at the top and tensioned by a turnbuckle fixed to the deck or to a raised lashing bridge. The rods run diagonally, so they resist the sideways racking of the stack.

The work is done by port lashers after loading and undone before discharge, to a plan calculated for that ship from the weights and positions of the boxes. It is the reason the declared weight of every container matters to people who will never see inside it, and why heavier boxes are stowed low. How large those ships have become is in the container ship sizes guide.

Cargo lashing is the part a shipper meets. A dry container has steel rings along its bottom side rails and, on most boxes, along the top rails as well; straps or chains run from the cargo to those points and are tensioned. Each ring holds only so much, so a heavy piece is held by several lashings sharing the load, together with timber blocking against the floor.

On a flat rack there are no walls at all and lashing is the whole of the securing: the platform has lashing points rated in tonnes, and the line will usually want to see how a heavy or out-of-gauge piece is to be secured before it accepts it. A vehicle is the everyday case — chocks at the wheels and a strap over each tyre to the rings, as set out in car in a shipping container. The accepted reference for all of it is the CTU Code, the IMO, ILO and UNECE code of practice for packing cargo transport units.

The usual mistake is to pack a container tight at the doors and assume the steel will do the rest. Side walls and doors are built to keep weather out and to resist an evenly spread load, not to stop a machine or a stack of drums that has started to slide. Cargo that breaks loose can burst the doors or go through a wall, and the damage to the box, to neighbouring containers and to the ship is claimed from whoever packed it.

The second mistake is lashing to the wrong thing. Straps passed over a car’s bodywork instead of its tyres, or hooked to a part of the cargo that was never meant to take a pull, hold until the first heavy roll. Lash to the rated points, tension evenly, block and fill the gaps with dunnage as well, and photograph the result before the doors close.