Abstract: An apparatus for infolding and sealing the side and end bottom flaps of a carton includes a unique bottom side flap infolding system comprising flap infolding arms mounted to rotary cylinders for automatically infolding and supporting the bottom side flaps. The rotary cylinders are actuated by a sensor which senses the presence or absence of a carton in the apparatus. The apparatus also includes a unique assembly comprising downwardly inwardly inclined rollers mounted to the conveyor side arm assemblies to urge the carton downward toward the lower sealing head to assure a complete and continuous bottom seal. The apparatus may also include transversely adjustable guardrails, a hold down flange to maintain the carton against the packing plate and a carton urging assembly for urging the carton through the apparatus.