Immediately before the press infeed, the density profile in the mat is continuously measured with a weight per unit area scale. For this purpose, the weight per unit area scales used x-ray the mat. In this way, the layer structure and the distribution of the raw density over the board thickness can be monitored and fluctuations detected. At the same time, foreign objects with a high raw density (stones, metal, larger branches) are detected again. These can then be removed to protect the sensitive press plate from damage.