The side skirt of a car --- the portion of the lower paneling between the front and rear wheel wells --- may become cracked due to road conditions, driving speed or other stresses. You can repair the side skirt by using a plastic welder or soldering iron to melt the two pieces of the side skirt back together. The procedure is rather simple, requiring concentration and tools that you can obtain from the hardware store.
Clean the area with a degreaser to remove grease, wax and road grime.
Sand both sides of the crack with 80-grit sandpaper. This will remove shards of paint that are sticking out and facilitate adhesion of the two sides.
Align the two sides of the crack together. "Tack" the crack by welding a small spot with your plastic welder or soldering iron at the end of the crack. This will ensure that the rest of the crack will hold together when you are welding it.
Push the tip of the welder at an angle into the crack and weld it. Start at any spot on the crack; allow the plastic to melt together.
Allow the plastic to harden. Paint a thin layer of epoxy on the back of the crack to further reinforce it.
