An apparatus for applying a marking to an elongated sheet material is provided. The apparatus includes a processing machine through which an elongated length of the sheet material is passed. A marking system is arranged to apply a marking to the elongated length of sheet material passing through the processing machine. The marking system comprises at least one spray gun and a pump for supplying marking fluid to the spray gun. The pump is operable at selectively variable speeds. A controller controls the speed of the pump based upon a speed at which the sheet material is passed through the processing machine.