A conveyor system includes an elongated vacuum plenum having an interior defined between upwardly and downwardly facing surfaces between opposing ends. A slot defining a portion of a conveyor path is formed in the plenum and extends from one end of the plenum at the upwardly facing surface toward the other end and the downwardly facing surface. A plurality of conveyor modules forming part of an endless loop are received in the slot and move along the conveyor path. At least some of the modules have at least one opening in fluid communication with the interior of the plenum. An object disposed on at least one of the modules is held against the at least one module by a vacuum in the interior of the plenum as the at least one module moves along the conveyor path from the upwardly facing surface toward the downwardly facing surface.