case may be in the course of its path of flow through the cylinder side gap 27 the blast air detaches the air boundary or layer entrained by the drying cylinder and thus prevents its infiltration into the inlet gore 22 the air wipe off means 25 at the inflow side edge 24 of the first wall means 21 deflects away a significant portion of the air boundary layer at the support band means 18 tending to otherwise flow toward and into the inlet gore 22 the previously described divergence in and of gap 23 creates a vacuum within such gap 23 during running of the support band means 18 and the paper web 16 this created vacuum in turn serves to hold the paper web 16 in full contact against the support belt means 18 further the supply of blast air which flows out of the opening or passage 29 and into and through gap 27 also has an effect on the opposite gap 23 that is as such blast air is ejected through slit or opening 29 and flows past the cylinder end of channel means 33 a suction effect is created at such cylinder end of channel means 33 causing at least a substantial portion of the air as may be in gap 23 upstream of channel means 33 to flow through the channel means 33 and into gap 27 to be swept away by the blast air from passage means 29 further the direction of flow of blast air out of discharge passage means 29 causes the creation of a reduced pressure or partial vacuum in gap 27 generally in the area from passage or outlet means 29 and extending into.