So I stripped all the original carpeting from my car... 8 years ago. There was the carpeting, and some other stuff underneath it that the mice like to play with. What I DONT know is what layers SHOULD be under my carpeting, and what function they serve. I have heard that there is mass-backing, jute, underlayment... I would have to guess at some point at least a couple of those terms are redundant. What layers SHOULD be on the floor of my car?