Door panels can suffer greatly from moisture, use and just plain old age. If your VW door panels are less then presentable, several options are available for replacing them. You can buy new door panels or make your own, which is not complicated, although it may take a few tries to get them right.
Lay your old door panel on top of your Masonite board. Carefully trace around the door panel and all of its interior openings (for the door handle, window ratchet and arm rest) the tip of a box knife to create a pattern. Remove the old panel and cut the pattern out of the Masonite board.
Transfer all the clips from the back of the old door panel to the same location on the new panel. You may have to cut a small slit in the new door panel and push them through, adding a drop of craft glue to the anchor legs of the clips to hold them in place while you finish the door panel.
Unroll your headliner foam so it is flat on the ground. Place your pattern on top of it. Use scissors to cut the foam to fit your panel. Turn the panel over so the part that faces into the car is on top. Spray the entire piece with adhesive and press the headliner foam into place. Let this dry for 20 minutes before continuing.
Cut out the fabric that you want to cover your door panel, making sure to cut the pieces at least 1/2 inch wider all around than how you want them to fit together. This will allow you create seams and edges. Lay the fabric as you want it to go on the door panel and make sure it is exactly the way you want it before going onto the next step.
Begin to attach your fabric to the headliner foam. Wherever you have two different types of fabric meeting, fold the edges so the seam is neat and flat. Open your stapler (a regular desk stapler is perfect for this) and staple the fabric through the foam to the board, then fold the fabric over the staples (like you are binding a book) and use the spray adhesive to attach the rest of the piece. When you are done, you should not see any of the staples because the fabric is folded over them.
Use a piece of vinyl edging to finish the door panel. The edging is preformed to wrap around your piece, simply open it a bit with your finger and push the edge of the door panel in between the two sides. You can either use spray adhesive as you go to attach the edging to both sides of the door panel or staple it on as you go.
Push the door panel into place, making sure the clips on the back side firmly attach to the car door through the small holes moulded in the door for that purpose.
Add a 6-inch-wide strip of thin auto carpeting to your door panel covering; this will help to block road noise. Most clips work in a similar fashion to a metal paper fastener, with the clip that will go into the door on the backside and the legs bent flat against the front, where they will be covered by fabric. Some clips simply glue to the back face of your door panel. If you have lost any clips, buy a replacement set at your local hardware store.
Open and shut the door a number of times and try to peel your new door panel off with your fingers using gentle pressure to simulate stress the panel will be under while driving. You do not want the door panel attached loosely, or it could come off while driving and interfere with your operation of the car.