Timber and other building materials can also be classified as deck cargo, along with things like prefabricated materials for construction. Deck cargo can be carried in containers in some cases, while in others, it may be lashed directly to the decks of the ship and covered with protective materials.
The First Mate mathematically calculates this, taking both the load line and the depth of different ports into account, and writes out a cargo plan. In the deck crew, the Second Mate is the navigator.