To repair a dent in a steel door, buy auto body filler at an auto parts store and follow the label directions. With most types, you sand down the dented area until you reach bare metal and then apply the filler in thin layers to build up the patch. When the filler is flush with the surface of the door, sand it smooth. Prime the patch with 100 percent acrylic latex primer, and then paint the entire door with 100 percent acrylic latex paint.

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