horizontally oriented spike rollers 7 in this forming box there is illustrated an inlet pipe 6 in the end wall 10 of the forming box in that side which is directed against the transference or movement direction 11 of the forming wire the inlet pipe 6 can be established in the opposite end wall 10 opposite to the inlet opening 9 of the inlet pipe a rebound plate 18 is established the rebound plate is mounted on adjustable seats 19 20 hereby the angle of the rebound plate can be adjusted so that an approaching cloud of fibres 21 can be directed substantially upwards according to the arrow 22 or substantially downwards according to the arrow 23 the rebound plate can be adjusted by means of thread connections 24 25 the rebound plate 18 can thus be given an angle position and can simultaneously be established in a shorter or longer distance from the inlet opening 9 as an alternative to the inlet pipe 6 the fibres can be introduced from the top of an upward open fibre box from the top as indicated by the arrow 26 in the shown embodiments the inlet openings 9 is indicated as circular openings however the transference opening can be an elongated cleft and the terminal part of the transference pipe 6 can in such a situation have form of a fish tail hereby is achieved an introduction of.