Abstract: Method and apparatus for making composition board having a planar surface and legs by an extrusion process from its constituent materials wherein there is provided an improved agitation mechanism for insuring the uniform dispersion of constituent material in the legs of the mold. The improved mechanism includes a plurality of pairs of agitation fingers, each pair adapted to oscillate in opposite directions about the same axis. Separate rack and pinion arrangements control the oscillation of respective fingers of the pairs. A pair of hydraulic cylinders controls the movement of the racks, the pinions being coupled to the fingers. The hydraulic cylinders are arranged in a control circuit, the operation of which is timed by a flywheel on the extrusion apparatus. The improved mechanism includes means for adjusting the timing of the finger oscillation relative to movement of a piston driven by the flywheel for optimum operation. Density of the legs of the board is controlled by controlling the timing.