I designed this bracket that allows joining 2 boards at a right angle to create a barrier preventing my dog from losing toys under our entertainment center. I got tired of playing fetch myself so wanted to create a boundary using 3x1 wood (18mmx61.25mm actual size).

Decided to make these corner clips instead of using screws so I would not have to move the entire piece of furniture to vacuum underneath as I had cut the wood to fit snug. There are screw holes available to attach to one board if desired.

Profile is for PETG but could easily be made from PLA if it won't receive too much abuse. I suppose ABS/ASA would have been even better but I don't currently have an enclosure.