The exterior door in garage is rotting at ground level. I hope I don't have to replace the whole door frame. Starts at ground and works up the jaw about 4 inches.
If it's just the one side, you can repair the jamb by purchasing a new piece of jamb stock. You can either replace the entire leg, which will require removing the frame from the opening or you can replace the damaged section. Replacing the section will not be a strong as replacing the entire thing, however a 6" patch isn't going to affect the integrity of the door.