Arrange two 3-by-3-by-80 inch wood posts on the ground, parallel to each other and about 29 inches apart. Set 20 35-inch, 2-by-4 boards on top of the posts and space them evenly apart from each other. Adjust the posts so that the ends of the 2-by-4s, which are the mattress support boards, are flush with the outside of the posts.
Drill two holes down through each mattress support board and into each post, for a total of 80 holes. Set 3-inch wood screws in these holes and tighten them completely to finish the bed frame.
Drill a hole through the top of the bed frame in each corner, about 1-1/2 inches from each edge. Screw an eye-hook with a 1-inch eye into each hole, tightening it until the eye touches the wood frame. Set a 1-inch-diameter carabiner into each eye-hook.
Use a stud finder to locate the ceiling joists or beams. Mark a location above each corner of the bed where a chain can be installed. Drill a hole into each marking and ensure that each hole hits a wooden joist or beam squarely.
Thread an eye-hook into each hole and tighten it securely until the eye touches the ceiling surface. Place a carabiner into each eye.
Hang a length of chain with 1-inch links from each ceiling carabiner. Close and lock the carabiners. Lift the bed with the help of an assistant and attach the other ends of the chain lengths to the carabiners attached to the bed frame. Close and lock those carabiners to secure the bed to the ceiling.
Adjust the height of the bed by raising or lowering the carabiner attachments to the chains by the necessary number of chain links.