air through the foraminous conveyor 24 in the disclosed apparatus strands of glass fibers not shown are received from a creel or the like in choppers 38 the chopped glass strands are then received in the hood and directed downwardly toward the conveyor 24 by gas passing through the inlet holes or ports 40 the construction of the creel choppers and ports are well known in the art and disclosed in the above referenced u s pat no 2 719 336 in the apparatus of this invention a plate 42 is located immediately below the foraminous conveyor 24 and is supported in the hood parallel to the conveyor on suitable supports 44 as shown in fig3 and 4 the plate includes a plurality of circular apertures or holes 46 through the plate and perpendicular to its faces the apertured plate thereby provides a substantial pressure drop across the conveyor as will be described more fully below in the disclosed embodiment the holes are spaced equidistant in the plate and define less than fifty percent of the total area of the plate for example 3 16 inch holes on 3 4 inch centers provide a sufficient pressure drop across the conveyor for the purposes of this invention the plate should also be located from the foraminous conveyor by a distance which is less than the diameter of the apertures as more fully described below in the method of this invention using the apparatus of fig1.