A Bunk

1. One of a series of berths or beds placed in tiers.
2. (nautical) A built-in bed on board ship, often erected in tiers one above the other.
3. (military) A cot.
4. (US) A wooden case or box, which serves for a seat in the daytime and for a bed at night.
5. (US, dialect) A piece of wood placed on a lumberman's sled to sustain the end of heavy timbers.