Here is my design for the 3dpn spool contest!

I tried to go simple with it, my idea is to have a section that holds onto the 1"x2".  The slot cut out allows for the brace to fit onto the 1"x2" without having to move any of the spools! 

I wanted to keep the spool parallel with the shelf.  This way you could position this spool holder directly above the printer you are using and the filament should feed straight down and allow for the machine to be farther (or closer) than if the spool holder was perpendicular with the shelf. 

The holder is designed to print flat for maximum strength in a single print.  It must be printed with supports but they're aren't many. I placed supports under the elevated side (required) and under the round section (optional) for appearance and smoothness.

Once you load the stl into your slicer, you need to rotate the 
X Axis 90 Degrees
Y Axis 225 Degrees.
I'm not sure how to fix the axis, only been printing a month!

Hope you enjoy this simple but effective design!