File:FieldBunk.jpg
Bunks in the barracks area of Crow's Nest military base.
A Field Bunk is a pad for Marines to sleep on in conditions that are not UNSC standard, which means it's a makeshift bed used during war times when actual beds are not available. For easy portability, the bunk can collapse, and can be brought to new locations when needed. The actual bunk is no more than some simple padding for the mattress, and is sometimes equipped with a pillow and sheets for the user.