The present invention relates to a method and an arrangement in a cardboard creasing machine performing creases on a cardboard blank web. The web has a width of at least two lanes of blanks in parallel to each other and comprise in at least one zone per pair of lanes an area where intentional creases on both are made transversally to a feeding direction of the machine. The crease-lines are on the male side interrupted to provide a longitudinal seal strip to an edge of each blank to become. The cardboard web is in a limited area of such an interruption intentionally and positively lifted and supported from the side of a female crease die to a level in between being in line with to being above an outermost surface of a female crease die roller of the machine.