Abstract: A special blank having cutouts at its side margins and a series of cutouts at its ends may be folded into a box having stiffening ribs in its bottom wall. That construction makes it especially useful as a box or tray for carrying produce, particularly when that produce is packed in standard berry boxes. Combined with a pair of end wall members, the folded blank provides a berry tray of the kind that will nest one in the other and is conveniently stacked in many-tiered stacks. The tray construction is such that it can withstand very high humidity environments, even when the construction material is corrugated paperboard. In the preferred form, the end members, or wall stiffeners, are formed of plural layers folded into a shape that is triangular in cross section so that the base of the triangle forms a shelf for supporting upper trays of a stack. One layer of the end member is notched to straddle the strengthening ribs. The other is not.