A corrugated box making machine has a vacuum transfer mechanism for moving corrugated boards along a path of conveyance including stations having printing and die cutter mechanisms which operate on the boards. The printing mechanisms include a print and impression cylinder, the latter being mounted in a vacuum housing that also holds drive rolls for moving the boards along the path during which the boards are held against the rolls by vacuum in the housing. The latter is movable substantially above the print cylinder to provide convenient access for maintenance of the print cylinder or replacement of its printing plates.