Yes, the interior plastic rear quarter panel. At the bottom of the panel where the rear seat meets up with the panel, there are 2 holes. One large one that looks to provide access to the quarter window adjustment and a small one that I believe is for the screw to secure the bottom of the panel. Both of these holes are not visible when the seat bottom is in place.
As 72cudaman said, there's a bracket of some kind that goes behind the panel that gives it rigidity. With out it, there's nothing for the screw to secure to. I probably have the parts around but would like to see a picture of what it looks like.
Thanks.