The top surface of the holder (3) has an outlet for a contact agent which is conveyed out of the outlet by a conveyor. A feeder pipe (8) is connected to the outlet. The outlet is in the form of a gap (7) crosswise to the direction of the movement of the conveyor belt (1) and positioned in the front part of the holder. A suction groove (11) on the top side of the holder is connected by a pipe (12) to a vacuum producer. A cooling plate (4) in the holder incorporates ducts (6) containing coolant.
