Abstract: The tool has a sheathing plate (34) having an outlet opening (39) for a spackling composition, to which outlet opening (39) a pressure line (12) for the forcing-in of a sealing composition can be connected. In order to reduce the time required for the repair process, there is provided, alongside the outlet opening (39), a second opening (43) which is closed off in air-tight and pressure-tight manner by an elastically deformable flat-shaped article (53) which can be inflated in the manner of a balloon; a chamber (50) adjoining the second opening (43) on the rear side; and the chamber (50) can be connected to a source of pressure in order to inflate the flat-shaped article (53) in the manner of a balloon.