For my diorama / Modelrailway i made this Ferist to use it for a tunnel entrance, sice is 70mm wide and 20mm depth. The step is for a 4mm plywood base of the road on the other side it is 5.5mm because the base plate of the tunnel was a bit thicker. 0.5mm are added for plaster to smooth the road and paint.
In the cross section you could see how the model is created to give a strong print, i flushed the chambers with diluded black paint before painting the rest to give an illusion of depth.
i added a second, smaller model with 70x20x4.5mm bottom wall has 2mm thickness to be sanded down a bit
Only for Private Use. 3D files or 3D printed Models could not be given away for free or be sold!