Here’s the genesis of my tomato tree, to hold four buckets that are cheaper than a Topsy Turvy.
The verticals are three-quarter inch
(the trunk of the tree is not in the picture)
The crossbars are half-inch
and they slide right through the openings of the bigger fittings
The orange caps are to protect the threads. The end-caps will keep the buckets from sliding off.
And here it is out in the garden, assembled but not standing
The hole needs to be another foot or two deeper, but I had reached the limits of post-hole digging as I knew it. Talking to my friend, I should have used water to soften up the hard dirt at the bottom of the hole. Oh, well – I’ll get there eventually.