I designed this to support removable crossbars for the ceiling of my modular painting booth. It supports the weight of 6mil plastic sheeting which covers a PVC structural skeleton. Assembled, the structure forms a cube 8 feet on a side but is designed to disassemble as a pile of straight PVC tubes for storage. I began the design with robustness and resistance to inadvertent damage when handled and so deviates from the typical "welded tube" designs more commonly seen on PVC pipe fittings. This may be overkill, especially with the dangling 'clip' wall, but it works well and I'm not motivated to spend more time on alternate designs.

I print this on FDM using .2mm layer height with PLA. You can adjust wall line count to adjust stiffness of the 'clip' functionality. Using 2 wall lines results in a light to moderate 'clipping' action with little assembly / disassembly resistance. This is designed to print without supports when orienting with the yellow face (see images) on the build plate using a raft base. It might also print without the raft, but I haven't tried that. A little sanding is all that's required to remove the extra raft material after printing.