apparatus for manufacturing thermoformed plastics trays comprising means for entraining along a plane a thermodeformable strip proceeding through a heating station , a station for forming container cells in the strip , a station for filling with a product the cells and a station for closing the cells with a metal strip comprising wording relative to the nature of the contained product . the heating system consists of mutually overlying heating plates driven intermittently parallel to the feed direction of the thermodeformable strip . the closing station comprises guide means for the metal strip which accompany this latter tangentially above the thermodeformable strip so as to close the container cells . the guide means cooperate with a metal strip stretching device controlled by members for off center detection so as to elongate the strip and center the print on the formed trays .