What are these things?

I think all the big name tent manufacturers make them. But, I would guess they are intended for display purposes only. I don't know if they are for sale to the public.

They just velcro to the carpet as a substitute for stakes. My local REI always uses them with their display tents.

I'm sure some kind of velcro thingy could be made pretty easily

Pretty sure they are just velcro or something similar. Keep in mind however that velcro does not stick to all carpet types. The carpet fiber have to have "loops". I know, because I've tried setting up shelters indoors and velcro did not stick to my carpet. But it does stick to some carpets.

Velcro also sticks to many of my synthetic shirts…at least long enough to snag them!

Well sense I was there when this photo was taken . . .

You guys are right; they are reinforced nylon pads backed with Velcro. Outfitter shops use them to set up tents indoors on carpet.

Be forewarned though, the Velcro patches only work on commercial grade low pile carpet. Even then they don't work that great, only providing enough adhesion to loosely set up the shelter.

Thanks, all. I was hoping they were something more magical than velcro because I know velcro will not work on my carpet.

Guess I will have to stick to my trial and error approach in the field.

Tack it through the carpet to subfloor with small (perhaps finishing) nails. I doubt this would cause much trouble.

Or use some type of non-barbed hook to attach through to the carpet backing. Might need to spread force to larger area of backing.

I've never used it personally, but have heard some friends talk about using Gorilla Tape for this purpose. It's usually found next to Gorilla Glue in the same aisle as super glue. It's pretty strong stuff! I wouldn't think that it would harm the carpet, but just to be sure, I'd test it on a small patch first before slapping a bunch of it down.

The large patches of Velcro (or hook&loop) will hook onto the right sort of loop-pile industrial carpet with no after-effects. But sticky Gorilla tape down onto the carpet will probably rip off a significant amount of pile each time. That adhesive is aggressive!

Another suggestion is to use 2" thick gaffers tape. Permacel makes the good stuff. It holds well, doesn't rip out carpet when you pull it up, and best of it all, it doesn't leave a nasty residue behind as duct tape does. You'll need to attach a loop or hook to it somehow for securing the tent, but this stuff works great for securing electrical cords/cables to flooring so people don't trip over it.