Related Photo Galleries
The old-school way to fill trim holes in sheetmetal was to braze them shut. This requires some two-handed skill with a torch and brass fill rod but does work well. The more modern approach is to use a nonferrous backing plate (like this brass block) placed behind the hole (when accessible) and use short bursts with a MIG welder. Steve prefers welding from the back side since this leaves the exterior smooth and eliminates all but minor grinding.