Work box with movable side walls

The invention relates to a construction container for a device for producing a three-dimensional model by layers, comprising: a construction region on a construction platform, in which kinetic friction between the constructed layer and at least two side walls is reduced or substantially avoided during displacement of the construction platform to adjust the height of the construction region, the construction platform and the at least two side walls are displaced at the same speed wherein the construction container comprises a driving engagement on each short side for attachment to the Z-axis drive unit, the side walls of the construction container being movable in a construction direction, the movable side walls being displaceable relative to the two fixed side walls, and during the construction of the three-dimensional object, the movement of only the construction platform and the movable side wall in the construction container is a vertical movement, the movable side wall is not rigid with respect to the fee