is exposed both to the inlet and outlet sides of the application zone 46 as well as to the zone itself the roll is rotatably supported in a concave holder 64 at the upper end of the front wall 30 and at the outlet from the zone the surface 62 forms with the web a narrow orifice 66 in which a liquid seal is formed the cylinder is maintained in the holder by a curved surface 68 of a member 70 mounted on the wall 28 and the surface is provided with spaced channels 72 which extend between the chamber 32 and the application zone 46 are approximately 1 4 inch wide and provide about a 50 percent open area through the member the channels define metering slots between the chamber and the application zone and rotation of the roll in either direction at a controlled rate by any suitable means homogenizes and shears the coating material in the metering slots orifice and zone thereby to improve the viscosity of the material and the uniformity of its application onto the web the metering roll 60 also provides two additional advantages in a first instance the roll itself defines with the paper web the outlet orifice from the application zone thus controlling overflow from and providing a fluid seal to the zone it has been found that use of a rotating cylinder for an outlet orifice gives a particularly smooth and controlled character to the excess coating material returned to the main supply a second advantage resides in the fact that the speed and direction of rotation of the roll affords a degree of control over the rate of delivery of coating material from the chamber 32 to the application zone and from the zone through the orifice 66.