3 and created by the stream of pulp stock that is as should now be apparent as the flow of pulp stock is forced through nozzle passageway 10 from right to left as viewed in the drawing the stream of pulp stock flows against the depending portion of the upstream side of the shutter means 3 and in so doing applies a pressure thereagainst the resulting force of which tends to bow or move the shutter means in a direction generally away from surface 14 and thereby result in the product defects hereinbefore described the invention by providing what amounts to as an intermediate elastomeric means 6 for the application of a counter pressure and resulting counter force uniformly across the functional length of the shutter prevents the occurrence of such undesired movement by the shutter means throughout its entire functional length the elastomeric means 6 of course functions to transmit the entire force exerted by the support member 4 to the shutter means 3 with such transmission of force occurring in a manner as to apply it to the shutter means 3 uniformly along its functional length without adverse influence because of such factors as uneven surface conditions on the shutter means against which the elastomeric means 6 is acting as previously indicated in the preferred embodiment the elastomeric means 6 is of a hose like or tubular configuration and further is in fluid communication with a source of fluid pressure accordingly as generally depicted in the drawing with the support member 4 positioned as illustrated fluid under superatmospheric pressure can be directed to the interior of the elastomeric tubular means 6 and in so doing even increasing the pressure and resulting counter force against the shutter means 3 also further various embodiments and modifications.