Prefolded cardboard blank for folding closed packaging boxes of varying height and length, said blank comprising a bottom panel, two side panels, each joined to opposite edges of said bottom panel and a first end panel joined with a first edge to said bottom panel, with a second edge to one of said side panels and with a third edge to the other one of said side panels such that the first end panel and the side panels when erected from the bottom panel form together with the bottom panel a box having an open top and an open side, the first end panel having an end portion intended to form a first top panel, each side panel having an end portion intended to form at least one second top panel and a corner panel, the bottom panel having an end portion intended to form a second end panel and a third top panel, and each side panel having a crease line running at an angle of 45° upwards from a corner, where the edges of the respective side panel, the first end panel and the bottom panel meet.