Hard bunks can be built from an array of available materials. Here 2x4 construction was used for frames and supports. Be sure to allow plenty of room for people to turn over.

These bunks which can also double as shelves, were fabricated almost entirely out of plywood with 2x4 lumber used only to provide stifflness and prevent sagging. Braces can be installed either on top to keep people or objects from falling off, or underneath to make a clean appearance. Two adults, if they are very tired or mutually friendly can share a bunk space if the shelter were crowded.