Indexes are just the sheets of images that you are supposed to stick on the back of each stamp. Some people call them something else. I forget what.
I'm with you on the stamp a ma jig, mswhittaker. I never, ever would have bought one, but my SIL sent hers to me because she found it a bother to use and I absolutely love it. I use it all the time. It's one of my must-haves.