Using clone tool for photo restoration
The clone tool is used on photo restoration to cover over areas of the photo that is damaged. It used to take a small part of the image and clone it over the damaged area. Some photo restorations require a more advanced combination of this tool and the healing brush and spot healing brush. Basically the same sort of technique but it the healing tools use texture and tone as well, replacing the damage with a very clean patch.
You can cover quite a large area using this photo restoration technique, although care still needs to be taken to ensure then texture and tone and cloned patches are a good match to patch over the damage in the photo being restored.