Abstract: The invention relates to a broadsheet for constructing a box consisting of a bottom and side walls, characterised in that two opposite edges of the bottom (1) are extended by a first transverse strip (3) and a second transverse strip (4) which is foldable with respect to the first transverse strip (3), whereby a) the first transverse strip (3) is extended along both its extremities by a wing which results in angular supports; b) the second transverse strip is extended along both sides of its central portion (13) by a wing consisting of parts (14 and 15) with a folding line (16) in between, resulting in glueing surfaces meant to be glued together with above said central portion and with above said first transverse strip.