Abstract: An apparatus for forming and sealing a fin at a gabled end of each carton in a plurality of cartons traveling along a predetermined carton path is set forth. In accordance with the apparatus, each carton has a first plurality of opposing top flaps disposed transverse to the predetermined carton path and a second plurality of opposing top flaps disposed longitudinal to the predetermined carton path. The first and second plurality of opposing top flaps are adapted to form a gabled structure of the gable top container. The apparatus includes a first pre-folder for directing the first pair of opposing top flaps of each carton toward each other, thereby also causing the second pair of opposing top flaps to be urged toward each other. A second pre-folder is disposed downstream of the first pre-folder along the predetermined carton path for increasingly directing the second plurality of opposing top flaps of each carton together as each carton travels along the predetermined carton path.