Does anyone have some good solutions to keep dogs from under your pinball machines?

I have my first coming tomorrow and my fiance decided we should keep it in the living room instead of basement, which is awesome. The dogs like to play a little rough, especially under tables, though, so I'm a little worried they'll knock out a leg or something and it'll fall on them. Anybody have any experience keeping dogs out from under pinball machines?

Thanks guys. I'm usually gentle with machines in the wild because I like our ops in Pittsburgh, so I wasn't quite sure how much abuse the legs can actually handle. This helps a ton. I'll just have to triple check that the legs are solidly bolted on.

blondetall, my dogs are pretty comparable to yours, so that's awesome. Still think I'm going to look into the playpen thing; thanks for that too!