Cylindrical segments are constructed with a convex and a concave end. When the segments are assembled into a ring, the convex and concave ends fit together, and act as cylindrical hinges. Such segments are used for lining tunnels, for instance the metro tunnels in Budapest. The hinges allow a certain flexibility in taking up pressure from earth surrounding the lining. There are dowels in the faces of the segments that force the rings to align, but it is the earth pressure that finally stabilizes the tunnel lining.