I just rebuilt a large cage to protect blackberries from the wildlife. I used older "Canopy Fittings" and new maker pipe 4-way and 3-way (90 degree) fittings. I needed a new idea for door hinges, so I was wandering around the local Home improvement Depot and saw some big eye-bolts. I picked the size closest to the 3/4" tubing and it was a pretty good fit. I only needed 2 for a 6' tall door and mounted them on the frame. I fashioned spacers from some bakelite rod to provide clearance. Cutting a tubing connector in half gave two sleeves to keep the door in position on the eye-bolts. See the pictures. It worked great. And the 90 degree maker pipes are sturdy enough to keep the door square without any stiffening.