Door shell nut. Left.REGULAR CAB & CREW CAB. Right.REGULAR CAB & CREW CAB. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the Door Reinforcement Bar. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the Door Shell. Nut that fastens the Door Hinge to the vehicle. Lock. Reinforcement Bar. Retainer. Ring. Shell. Included with: Door Shell, Upper Hinge.