Innovations and developments in the types of cargoes carried in freight containers have allowed heavy, bulky items which were traditionally loaded directly into the ships' hold to be carried in cargo transport units (CTUs).

The IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units (CTU Code) gives advice on the safe packing of cargo transport units to those responsible for the packing and securing of the cargo and by those whose task it is to train people to pack such units. This publication outlines theoretical details for packing and securing as well as giving practical measures to ensure the safe packing of cargo onto or into CTUs.