on the upper side of the sealing rods 49 which marking works together with the edge of the opening 50 to indicate the length of the covered portion of the respective nozzle web 42 in addition clamp screws 52 can be provided to fix the positions of the sealing rods 49 furthermore with this apparatus the area of the nozzles subjected to compressed air can be reduced in size as desired from the outside toward the inside and can adapt to any desired shape and size of the glass panes if a particularly good seal of the nozzle openings is needed the sealing rods 49 can be provided with an additional sealing cross sectional shape 53 as illustrated in fig8 this sealing cross sectional shape 53 made from a rubber like material with a u shaped cross section is attached to the metal strip 54 in such a manner that the two side shanks of the shaped strip are directed against the direction of air flow and under the effect of the air pressure they act as sealing lips lying against the side walls of the nozzle web the attachment of the sealing strip 53 is accomplished by means of a flat strip 55 placed on the outside of the center web which.