Abstract: A packaging machine wherein an upper film is joined or sealed to a lower film at intervals between spaced articles being advanced on a conveyor, the seal being made by and between a vertically reciprocable, upper, heated, joining element and a cooperative, vertically reciprocable, lower abutment roller element. The abutment roller is at the plane of the conveyor, which is normally an endless belt, with the belt being there diverted around the abutment roller and around a drive roller engaging the abutment roller. The rollers and the heated element are on a carriage which is horizontally reciprocable in one direction with the belt and then back to a return position. The vertical strokes of these elements can be controllably altered during operation of the machine, to accommodate the article size, as can the horizontal stroke of the carriage.