You will need old computer keys (just use a screwdriver to pop them off the keyboard, a needle nose pliers, small magnets (I got mine at Michaels - use those coupons to get 40% off!) and hot glue.
The keys will have a "peg" sticking up from the inside. Take a needle nosed pliers and you can just twist of off - it will break without much effort.
Take your hot glue gun and "flood" the inside about half full with hot glue. Then "float" the the magnet on top. Push it down with the pliers so it is level with the edge of the key.
I made a bunch of these and have them on my file cabinet in my computer lab. The kids (and me) have a lot of fun spelling words out using the keys!
Such a fun craft to make as a gift - spell out a name or appropriate phrase!