Just do an image search for the word "sedan" or pay attention in traffic. It's an exterior panel so I don't think it can be very much structural. Maybe aerodyna

Just do an image search for the word "sedan" or pay attention in traffic. It's an exterior panel so I don't think it can be very much structural. Maybe aerodynamics though. Once you see it you can't unsee it and it starts to look very ugly very fast.