A device suitable for finishing and sealing the joints and openings of different surfaces is described here. The device includes a base, which is conical in its essence. The base has a collar to connect the device to the gun of sealant of finishing material; a holder is integrated with the base at an angle, a movable smoothing pad with a carriage is fitted in the holder, and the carriage is installed in a casing inside holder. In the working position, there is a space between the smoothing pad and the tip of the nozzle of the tube, so that the material which is applied from the tube to the surface can visually be monitored and thus the desirable quantity dosed during the performance of the works.