Abstract: Press racking, or lateral movement of the movable portions of a press, occurs in certain particleboard processes during heating and pressing of the panels. It is attributed to shingling of wood particles during the formation of a mat. To eliminate or reduce the movement of the press, the mat is subjected to rolling engagement by a relatively small diameter roll located between the forming apparatus and the press. The roll subjects the mat to a downward rolling pressure. The peripheral roll surface is in contact with the newly formed upper surface of the mat and has a linear speed and direction of movement identical to the speed and direction of movement of the mat support. A resulting wave action within the mat is caused by shear and displacement forces applied to the wood particles, such that the shingled nature of the mat is modified to reduce or eliminate resulting lateral movement of the press components.