Corner litter box for our Critter Nation cages. Got tired of the boxes being pushed out from the edge, and critters making a mess behind it. Accomplished this with the clearance for the cage tray and loops to constrain it to the cage walls. You'll have to print with supports because of both of these features. I use a zip tie through the loop to keep the box fixed to the cage, and don't zip it for easy removal for cleaning.