A container is opened at a warehouse and nobody can tell which of three purchase orders the cartons belong to. The marks were printed on direct thermal labels that went grey in a hot container, two of the orders used case numbering that restarts at one, and the packing list references numbers that no longer appear on the boxes. Nothing is damaged and nothing is missing, but the consignment sits in a hold area until it has been physically recounted.
A shipping mark is a block of information, and every line in it has a job. Consignee name or buyer's mark, the purchase order or contract number, destination port or place, case number in an x-of-y form, gross and net weight, and measurement. Country of origin sits nearby but answers to a separate legal requirement. Whatever the block says, it must match the packing list, the commercial invoice and the bill of lading exactly, because reconciliation at destination is done by eye against those documents.
Place the mark where it can be read without moving the carton. Two adjacent faces, usually one long side and one short side, so the block is visible whichever way the carton is turned, with at least three centimetres clear of every edge, seam and tape line, and clear of where strapping will cross. Pallets get their own placard on all four sides, at a height that reads from a forklift seat. A carton mark hidden under stretch wrap is, in practice, no mark at all.
Print method decides whether the mark survives. Direct thermal labels fade under heat and abrasion, which is precisely the environment inside a container crossing the tropics, so use thermal transfer or stencilled oil-based ink instead. Coated and waxed cartons reject inkjet. In humid trades a polypropylene facestock with an adhesive rated for the application temperature outlasts paper, and paper labels lift at the corners once condensation has been through a carton twice. Stencils on plywood cases need a contrasting painted background, not bare timber.
Handling instructions belong in symbols rather than sentences. ISO 780 gives the standard graphical marks, among them fragile, this way up, keep dry, centre of gravity, do not stack and sling here, and they work regardless of the language of the person handling the box. Written English alongside is useful but not sufficient. Use the symbols honestly: a this-way-up arrow on every carton teaches handlers to ignore arrows, and a do-not-stack mark on a stackable carton wastes space you have paid for.
Country-of-origin marking is a legal obligation separate from the shipping mark, and it attaches to the goods or their retail packaging rather than to the export carton. Most destinations require it to be conspicuous, legible and permanent enough to reach the final purchaser, and several specify wording and position in detail. An export carton marked with the origin does not cure an unmarked article inside it. Check the destination rule per commodity before production, because remarking after arrival happens under customs supervision.
Regulated marks are not a matter of style. Dangerous goods packages carry the UN number, the proper shipping name, the hazard labels required by the IMDG Code, or by the IATA dangerous goods regulations for air, orientation arrows on liquid packagings, and a marine pollutant mark where it applies, with placards on the container itself. Solid wood packaging carries the IPPC mark for ISPM 15 heat treatment on at least two opposite faces, permanent and never handwritten. A wrong regulated mark stops cargo rather than delaying it.
Numbering discipline is what makes a consolidated shipment auditable. Case numbers should be unique and sequential across the whole consignment rather than restarting on each pallet or each order, and the packing list should read in the same sequence. Where several purchase orders travel in one container, give each order a visibly distinct mark block, and avoid order numbers that differ by a single digit. If a carton holds mixed items, the mark says so, because a warehouse finding two products in a single-product carton stops counting.
Prove the marking before the run, not after it. Approve a printed proof against the document set, then mark one carton, photograph it, and have someone at the receiving end confirm they can read and reconcile it. On a long production run, sample again mid-run, because ribbons run out and stencils clog. Where marking, remarking or relabelling has to happen after the goods are already made, it is warehouse work, and doing it at origin in Shenzhen is materially cheaper than doing it at destination.
