I can't figure out how to remove this strange rear fastner. I've tried to spin it and thought it was doing something but it seems it wasn't. Already broke 3 others off trying to get this cover off... The cover that is by the muffler and connects to the rear bumper. Under the car. Thanks, Higgins909
Keep spinning it counterclockwise. It's essentially a nut, threaded onto a long stud. Its convenient feature is that, while installing, it can just be pushed over the threads. Then you can just turn it a couple turns clockwise to cinch it down.