Although that's the real link (for post #19310), it doesn't work going to it from external sites for some unknown reason. 😒 Go to TomatoJunction.com, go to The Gallery, and look for a thread called QAGuys Garden (Wed May 06, 2020 3:14 pm). I think you'll have to register and login to see the pictures, too.
Basically, there are vertical poles in the middle of each of four horizontal poles (the are linked for foam a square), which vertical poles anchor it to the ground, and allow for the same thing to be placed on top to extend it when needed.
Anyway, now I want to get a bunch of PVC pipe. Those short cages look perfect for muskmelons in my garden (without any additions). In the case of my muskmelons, I like a short cage to increase productivity—not to reduce the space the plant takes up (although doing that is fine, too, if the fruits don't slip when ripe). It doesn't take much of a lift to seem to increase production quite a bit. Each horizontal pole is broken into two parts (in order to attach the vertical poles going down perpendicular to them).
You could take these cages apart at the end of the season, too, I imagine.