spread the pulse of air along the zone length of the sidewall these plenum boxes are so ducted as to transfer the air 84 with minimal pressure loss along a gradual internal radius from horizontal to vertical direction the air is directed into the finger ductwork 40 entering through the finger openings 40 a and pressurizing the finger cavities 40 b the finger ductwork 40 and orifice plates 42 are so designed to uniformly transform the higher pressure low velocity air mass into individual jets of high velocity that impinge the glass velocities are suggested to be in the 1500 to 5000 fpm range for manufacturing economy of the air system and optimized heat transfer on the glass sheet the airjets 85 scrub the insulating boundary layer of air at the glass surface introducing high temperature convection heat transfer the spent gas is continually displaced with a continuum of air jets following behind in the circulation system the exhaust path of spent air is designed to flow in a specific manner between each of the finger ducts 40 the exhaust path is generally split with u00bd of the supply flow exiting to each respective side of the finger duct 40 and evenly along the finger length the spent air follows the upward path of the exhaust stream 86 toward the fan inlets recirculating in the described pattern the heaters 50 52 shown in fig2 c are arranged in a specific functional orientation to the finger ductwork 40 the arrangement allows the spent exhaust.