WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
Install the rear side door opening carpet retainers to the vehicle.
Fig 1: Installing Rear Side Door Opening Carpet Retainers To Vehicle
Courtesy of GENERAL MOTORS CORP.
Position the door carpet retainer clips to the carpet slots and push down to secure.