Abstract: A device for mounting an independently formed closure upon an open-topped container wherein the container is stabilized by contents to constitute a stationary die, and with a forming die provided above said container for reciprocal movement toward and away from same. Said forming die contains a flat under surface for directing a flat closure upon the open upper end of said container and retaining same against inadvertent displacement; there being roller elements carried on said forming die for travel beneath the normally lower end thereof to direct marginal portions of the closure against said container and to hold same in such position to permit previously applied adhesive material to set.