After organizing and tidying up the instructables office a couple weeks ago, we realized we had an extra bookshelf that wasn't needed. I was bummed because I just bought a bookshelf for my room for $30 and the only piece of furniture I needed was a bed... but then I thought there has to be a way I could use it. I took the specs of the shelf and my twin size mattress was exactly the perfect size to fit on the shelf if it was lying down.
Thus, here is my awesome re-purposed bookshelf bed!
Step 1: Materials
Bookshelf - Free
Piece of plywood (1/4" thick, the same width and length of the bookshelf) - $30, you could use any flat board like thing that does not bend easily
Screws (8) - approx. $1
Contact Paper - $10
Screwdriver - already had
Drill - already had
Although you may not be able to find a bookshelf for free, check out yard sales and craigslist. You will be surprised how cheap you can get them for. They are often much cheaper than buying a used bed frame. Also, make sure the edges of the bookshelf are thick like this. If they are thin the bed will be flimsy and may not support your weight and it will be hard to attach the plywood.