Shipping guard for door edge is what it appears to be. They diodn't leave any of those in mine.... but I have worked in and out of so many dealerships, I'm certain that is the purpose for the plastic bit. Dealer lot protection and shipping protection.I bought a new 2012 XB about a month ago. I found this on the floor of the back seat. What is it for? I know it is probably a dumb question.