Couplings for extruded aluminum tubing 0.5" square outside with 0.04" walls

thingiverse

I recently acquired a collapsible trade-show display wall consisting of numerous 0.5" square aluminum extrusions with 0.04" thick walls, along with a variety of plastic components, rivets, and webbing straps. This massive structure expands to approximately 8 feet square by 30" thick, and collapses into a compact 1'x1'x3' shipping case. Over the years, several tubes had broken, so they were destined for recycling. I rescued it with the intention of drilling out the rivets and repurposing the extrusions to build various projects. To facilitate assembly, I decided to create couplings for different combinations. Update 07/01/19: I just noticed that I failed to inset the sides on one leg of each shape, which means that leg won't fit into the tubing. Sorry about this mistake; hopefully, you checked before printing any. I think it's fixed now, and I've also added rounded edges to make it easier to start them into the tubing. The 2-way-corner still lacks these features - I ran out of time just now. However, I'll add them soon.