The bolts holding on my rear license plate don't seem to want to come free. They just spin when I try to remove them. They are 10mm bolts. There is very clearly a nut of some kind on the inside that I can't get to and is why I can't remove the bolt.
I sprayed the bolts with PB Blaster to try to loosen them bit it didn't help. The vehicle is a 2007 Toyota Prius.