Abstract: The invention relates to a broadsheet from cardboard for constructing a stackable box with corner supports, which box consists in a usual way of a bottom and four side walls, characterized in that two opposite side walls of the box to be made from the broadsheet show extended parts which are folded according to parallel lines and this in such a manner that some sides of these parts which will form in a later phase a corner support are adhered by glue to an adjacent side wall while the other sides of the same parts or a portion thereof are provided with a fasteners which co-operates when constructing the box, i.e. amongst others when forming the corner support, with an analogous fasteners provided on the other adjacent side wall.