Abstract: A vacuum-type sheet transfer apparatus for a rotary printing press includes an air dam device formed by an elongated plate which is supported on the transfer apparatus housing and extends toward the surface of a transfer cylinder or impression cylinder of the press. Spaced apart openings are formed in the plate and have deflectable elastomeric flaps disposed in the openings to allow the cylinder gripper fingers to pass by the plate. An air dam or seal is formed by the plate to redirect the flow of air to urge sheets, including lightweight and heavy weight stock, to follow a preferred transfer path between the impression cylinder and the vacuum transfer apparatus.