This process relies on an engraved roller running in a coating bath, which fills the engraved dots or lines of the roller with the coating material. The excess coating on the roller is wiped off by the Doctor Blade and the coating is then deposited onto the substrate as it passes between the Engraved roller and a Pressure Roller. In this procedure, the coating material is measured onto the applicator roller by precision setting of the gap between the upper metering roller and the application roller below it. The coating is 'wiped' off the application roller by the substrate as it passes around the support roller at the bottom. The diagram illustrates a 3-roll reverse roll coating process, although 4-roll versions are common.In this coating process, an excess of the coating is deposited onto the substrate as it passes over the bath roller. The wire-wound metering rod, sometimes known as a Meyer Rod, allows the desired quantity of the coating to remain on the substrate. The quantity is determined by the diameter of the wire used on the rod. This process is remarkably tolerant of non-precision engineering of the other components of the coating machine.