How big a crash would be needed to bend the chassis on a car?

I'm just asking as I bought a clio 16v but it was in a wee crash a while ago, but it all got fixed up under insurance. Yesterday I noticed a couple of things which had me seriously pannicing thinking i'd bought a car with a bent chassis or something, but now think I have managed to explain all the things I noticed. The only problem I have is that the bonnet isn't quite right and is pushed too far back on one side.

How can you check if the chassis is bent or whatever?

I don't really know much about that side of cars so I'm just trying to check whats what. Is that what is meant when people talk about a car being put on a jig - to sort the chassis etc?

As I say, I now think mine is OK apart from the bonnet, but just wanted to find out more about it and get an idea of what would be required to cause that sort of damage.