OH! Well, the part that mounts to the roof is held on by a nut with sharp teeth accessible from under the headliner. You have to carefully pop off the "vented" plastic piece that secures the headliner, then you'll see the wires to the 3rd brake light and the FM antenna. Unplug the antenna mount from the inside and unscrew that nut with the teeth... no, don't use YOUR teeth...Reassemble!