It is not recommended to put anything between your vehicle seat and car seat and if you must, one layer is the maximum. There are however instances when in installations, I have used drawer shelf liner, cut to fit the car seats bottom, to reduce excess slippage in installs. I can count on one hand the amount of times I have resorted to that however. So in summary, abstain from using that or other similar types of products and if you *must* have a protective barrier (new car and such) use shelf liner at your own risk. There have been instances in hotter climates where shelf liner has melted to the vehicle seat. A simple towel can also add a protective layer.