This bracket is designed to mount an Arduino Mega + RAMPS sandwich to 15mm OpenBeam in what would seem like the least convenient position - sticking straight out from the beam. The idea being to solidly mount the print controller to the bottom-most beam under the print bed of a Kossel Mini. This significantly reduces the bulk of the wiring in the uprights (lots of heavy wires + a few thin -> a few heavy wires + lots of thin), and hides the rats-nest under the print bed. 
It's not particularly convenient for tweaking motor drive current, and you'll want to hook up an external reset button (if you don't already have a controller) but it looks much tidier.