There are usually five lug-nuts that hold these things in place. And it's important when installing these hubcaps, to tighten them from opposite ends.
Start with 12:00.... then 5:00... then switch back to 9:00... you get the idea.
You want to make sure these puppies are tight, and won't work themselves loose.. and uh.... hold on a second.
[what is it? I'm in the middle of a post here!? What!? What do you mean it's not a DeSoto hubcap?? it's a Costco Pumpkin Pie!? But it's huge... it weighs four pounds, dammit! Really? Are you sure?!]
um.... Never mind.