An apparatus for forming a layered mat of non-oriented particles in a particle board production process, said apparatus having a longitudinal dimension, a lateral dimension, and a vertical dimension, wherein said apparatus comprises: a source for providing a continuous stream of particles; a first set of rollers arranged at a first vertical level and capable of fractionating said continuous stream of particles into a first and a second fraction of particles, wherein said first fraction of particles has a smaller average particle size than said second fraction of particles; a second set of rollers arranged at a second vertical level, lower than said first vertical level, to receive said first fraction of particles, said second set of rollers being capable of further fractionating said first fraction of particles according to size; and a third set of rollers arranged at a third vertical level, lower than said second vertical level, for receiving said second fraction of particles, said third set of rollers being capable for further fractionating said second fraction of particles according to size; wherein said apparatus further comprises a receiving surface, movable along the longitudinal dimension of the apparatus, and arranged to receive said fractionated first fraction and said fractionated second fraction from said second and third set of rollers, at different longitudinal positions on said receiving surface; wherein the rollers of said first set of rollers and said third set of rollers are pin-type rollers comprising multiple pins or rods or bars arranged in substantially parallel relationship to the axis of rotation of the roller, such that said pins, upon rotation of the roller, move on concentric circular paths around the axis of rotation of said roller, or having rows of pins arranged, seen in a cross-sectional plane normal to the axis of rotation, on straight trajectories from a first, radially more outward position towards a second, radially more inward position. / a source for providing a continuous stream of particles; a first set of rollers arranged at a first vertical level and capable of fractionating said continuous stream of particles into a first and a second fraction of particles, wherein said first fraction of particles has a smaller average particle size than said second fraction of particles; a second set of rollers arranged at a second vertical level, lower than said first vertical level, to receive said first fraction of particles, said second set of rollers being capable of further fractionating said first fraction of particles according to size; and a third set of rollers arranged at a third vertical level, lower than said second vertical level, for receiving said second fraction of particles, said third set of rollers being capable for further fractionating said second fraction of particles according to size; wherein said apparatus further comprises a receiving surface, movable along the longitudinal dimension of the apparatus, and arranged to receive said fractionated first fraction and said fractionated second fraction from said second and third set of rollers, at different longitudinal positions on said receiving surface; wherein the rollers of said first set of rollers and said third set of rollers are pin-type rollers