It goes behind the door where the wiring harness feeds over from the passenger compartment up over into the rear area of the car. If you raise the rear deck (like to put the top down) and look in there you'll see where the wiring harness comes through. That rubber piece is basically a sound insulator to keep noise from the rear compartment from coming into the passenger compartment. It doesn't just pop back into place and there is nothing really holding it in place. I had to put glue around the contact edges then insert it in place. Let me know if you don't understand and I'll get a photo and post it here for you.