How to ... flatten bottlecaps

Once you've saved up a bunch of bottle caps, you need to flatten them. Squidoo has a tutorial showing how to do this with either a Sizzix machine (a what machine?) and a converter plate or a hammer. I don't have a Sizzix machine -- I don't even know what it is -- but I do have a hammer. And if I had a hammer (no, that's something else ...) Anyway, Squidoo also shows how to flatten bottle caps with a hammer here.