Gas Cap

Like I said....don't ask me how I know off this..
When I worked at the C/P dealer, I had a customer's Duster out for a road test and I had to put some gas in it.
It was in the middle of a snow storm and the only place I could put it was on the back window. When I made a left turn onto the street, I heard this terrible scraping noise. It was the cap slidding across the ice on the window.
I learned my lesson.