I was looking for a way to store filament spools. 

This part prints with no supports required.

For my first shelf, I used 1" x 4' Dowel rods. For the four legs, I just cut two of the Dowel rods in half. (Total of 8 dowel rods for the shelf pictured) The screw size doesn't really matter. It's just something to secure the dowel to the bracket.

For my second shelf, I used the 3D printed dowel rods are from here.