The ones my wife bought were slid into the upright pipe and just had a chain holding them from falling out. When you go to set them down the feet would keep turning on me, kind of a pain when you are doing it yourself. Also the ones we have have the legs on the end of the panel, so everytime you make a corner they have to be turned just right so they don't overlap. Sounds like I'm b%^&ching I know, but when you have to get on and off the tractor a couple times every time you set a panel it sucks and put a sour taste in my mouth.
I'm sure there may be better thought out and built ones than what we ended up getting, but I like my fixed position legs better. imo