Freightliner Rear Axle Hubcap Removal

That looks to me like a "wheel simulator." Generally they're held on with two of the things that look like lug nuts (the others being fakes attached to the cover). These two real nuts are generally marked with a little dimple or something on the top, but I find it just as easy to tell which is which by gently rapping them with the ratchet handle and listening to the plink sound; there's a distinctive difference in tone between the fakes and the real ones.

I could be entirely wrong about the setup, too.

Edit: I am entirely wrong about this setup.