Wall cranes are cranes, which, on 1 side, run along wall-mounted rails and of which the other end is freely suspended. On the wall side, two rails mounted above one another whereby the upper rail moves the crane in a vertical direction.  The lower rail is mounted sideways against the wall and used to support the crane horizontally. Such cranes are frequently used when you are required to cover a large area in 1 direction whilst movement of the other axis is limited.  For instance, when transporting semi-finished products through a hall where a series of machines is lining the wall.