What you'll need:
A computer with 123D Make (it's free!!!)
A material, I used corrugated cardboard, Easy to find for free.
Hot glue gun and hot glue. Unless you plan to use it all the time, go to the dollar store and get the gun and glue for a few bucks
Scissors, you really don't have a pair of scissors? I'd get a decent pair that is sharp enough to slice through some cardboard. You could use an exacto knife if you'd like
A 3D file. If you don't know how to make one, you can easily find one for free online.