Squeeze out equal amounts of material from each of the two tubes included in the package onto a clean work surface. Mix the portions together thoroughly, using a disposable paint stirrer or wooden dowel.
Clean the area of the crack thoroughly with household cleaner and and allow it to dry. Remove any paint, primer or rust with coarse grit sandpaper.
Roughen the surface to be welded, using the fine grit sandpaper.
Apply a bead of the weld along the length of the crack, using a putty knife or wooden dowel. Fill the area completely and lightly smooth the surface.
Remove any excess material around the repair site with a rag.
Allow the cold-weld to cure for 4 to 6 hours, and then use fine sandpaper to sand the compound smooth and even with the surrounding area.
Wipe away any loose material with a clean rag.
Allow the cold-weld compound to dry completely overnight and apply a coat of paint to blend the repair with the surrounding surface.