Other obstructions possible in a tweendecker’s cargo compartments are columns or pillars supporting overhead decks. It is essential to check on the location of such obstructions if intending to use a vessel for large, bulky cargo. Some tweendeck vessels are fitted with ‘cargo-battens’ (strips of timber fixed at intervals usually horizontally but very occasionally vertically) along the sides of holds and tweendeck spaces, and designed to keep bagged and baled commodities from being damaged by touching the sides of a ship which are invariably wet through condensation and/or slight seepage through microscopic faults in the plating. Cargo-battens also increase ventilation and reduce damage from moisture or sweating. However, they are frequently damaged and have to be removed entirely and stored elsewhere when handling a bulk commodity. Since they are expensive to maintain in good condition and it is labour intensive to keep repairing and removing cargo-battens, it is nowadays unusual to find tramp general-cargo ships fully equipped with this facility. Instead cargo-nets might be used, but more commonly cargo is protected when necessary by a combination of kraft-paper and other dunnage material fitted sometimes by the crew but more commonly by shore stevedores as loading progresses. Dunnage can be of various material but is usually loose wood of various kinds and sizes laid at the bottom of a cargo hold to keep lower-stowed goods clear of bilge water and from obstructing drainage, and also wedged between parts of the cargo to keep the stow secure and safe (e.g. for the carriage of drums). Certain trades traditionally use other, local materials for similar purposes, ‘cargo-mats’ and bamboo, for example, being utilised as dunnage material for the export of bagged rice from South-East Asia.