As in permenantly installing it into a car? Or just sticking it on the backseat while you move or something?
But back in the old days you used to have to "park" your hard drives so that the heads wouldn't move. But now you don't have to worry about that so much.
I drove 1700+ miles with two rigs in my backseat and got them to my house in NJ hooked them up and they fired right up.
I have a handle on the back of mine (back of the sidepanel). I put it on it's side and thread a seatbelt through the handle and it's perfectly secure. Works very well.
However, if you're talking about putting one in a car permanently, I don't know.
I usually put it on the floor in the backseat, w/ the front passenger seat pushed back to secure it. Or I lay it down on the back seat itself. Never had an issue.