The cartoner has been designed to form cartons from blanks, whereby the formed cartons have tapered concave sides. A unique series of elements, including capture lugs which hold and “bow” the carton blank, together with plow rods and oscillators which have curved metal plates are used to “pre-break” the score lines of the blank. Travelling pressure blocks having convex outer surfaces are used to press the concave sides of the carton while hot glue dries, whereby the unique, tapered cartons are properly formed.