Hi
I must admit I don't know the correct name for them, but I do know they are next to useless.
I think I have used mine twice, once for trying to prevent a case of marble from tipping and once (still) for holding my 2nd spare wheel. The problem is what to use with them ?

I found these , but they are only so-so, and you have to thread the strap through each time & they won't take 2" straps, any more than the rail will !.