Exterior panels that are bent at the edges of the frame and joined to the interior door frame by welding (or, in some cases, gluing) are called door skins. If the inside of the door frame is intact or if a replacement door is too expensive or unavailable, this repair can be very cost-effective. Since manufacturers and models vary slightly, the following serves as a general reference and assumes that the car door is disassembled. To determine what needs to be disassembled, examine the hinges. Some models with welded door hinges require the use of a tool to remove the hinge pin.
Original liners usually cover the entire door from top to bottom, but replacement parts usually cover only the bottom of the door up to the window level and are much less expensive. For many popular models, repair parts for the bottom of the door (rust repair panels) are available. However, the extra work involved in cutting, welding and filling is usually not worth it.
Changing the door skin
When cutting, a close examination of the ground edge will reveal the door frame and outer skin layers. Remove the outer skin once the entire edge has been removed. Later models may be equipped with a side impact bar or reinforcement strip that may also be attached to the outside of the body. There will likely be some adhesive in some spots and some spot welds that will need to be finished with the grinder. Peel off the remaining inner strip after removing the outer skin, then use the grinder to smooth the rough areas.
Before placing the replacement skin over the existing skin to check its fit, level the notched edges of the door skin with a hammer and panel block. The margins of the new skin should be bent securely with a hammer and block after they have been properly aligned.
It may be worth trying some additional metal cutouts first, as it takes some practice to perfect them. To avoid damage, clamp the outer skin and door casing with the block tilted so that only the edge is supported and there is little contact with the skin. Using a flat hammer (ideally a panel hammer), firmly bend the inside edge of the door against the casing.
A variety of door stripping tools are available, from inexpensive ratchet and roller models to simple "crimping pliers" that can leave scratches on the surface, but for a one-time procedure, a little patience with some minor surface damage is usually best.