Abstract: The invention is to shake the upper run of a Fourdrinier forming fabric of a paper machine by imparting vibratory motion, in a direction transverse to the machine direction, to light-weight foil blades mounted at the dilute end of the Fourdrinier section. The foils, which are in contact with the fabric, cause the upper run to vibrate in the same transverse direction, thereby shaking the stock and improving paper formation. It is preferred to vibrate the foils at a frequency close to the resonant natural frequency of the upper run of a fabric or a harmonic thereof. All or part of the top surface of some of the foils, which contact the upper run of the forming fabric, may be coated with a material having a relatively high coefficient of friction to increase the frictional contact between the upper surface of the foil and the forming fabric.