Had to add my 2 cents late as it is
Waaaay back some 50 odd years ago, the first metal shop project I was required to make was a pair of axle stands. We had to use pipe, slit one end into 3rds making 3 legged axle stands. The instructor would test them in the shop hydraulic press to 5 tons, if they failed so did we. Mine passed!! LOL
Back then we didn't have manufactured axle stands, engine hoists, engine stands, tow bars, and etc, that could be bought at the local auto parts store. If we wanted these items we had to have them made or make them ourselves. So I learned how to and made many in my life time.
Over the years I have built a dozen or so for myself and friends using square tubing that can go as high as 30". The metal supplier here sells slide in trailer hitch tubing that has the proper size and wall thickness to allow them to fit snugly making for a very stable axle stand. I actually have made 2 types, one with a 3/16ths flat bottom which is great on asphalt and dirt, the other is with spreaders between the legs allowing the legs to have something to dig in with on concrete. Personally I prefer the flat bottomed ones as I get 5 points of contact as the center tube sits on the flat bottom plate and has 4 angle iron legs to the corners of the of the plate. Word to the wise, tack weld the center post ONLY then weld on the outrigger legs before welding the center as it will warp the bottom plate so don't over weld it.
Square tube is great for making 4 legged axle stands as you only are cutting on the flat surfaces not having to divide round pipe into 1/3rds and try to make the cuts with a hand hacksaw without hitting the other side of the pipe. Not to mention drilling the lock pin holes on a round surface and getting them centered correctly.
We even used one of mine to support the keil at the bow on a 60 ton yacht I was working on in the yard once so the boot stripe could be painted on and it never failed.