The stone (101) has cuboid outer sides (105, 106), a flat upper surface (108) with respect to an opposing base (102), a front side (103), and a back side (104). A sloping contact surface (110) is provided in the front side. The front side includes a portion with a radius of curvature, and another portion between the former portion and the upper surface, where a radius of curvature of the latter portion is smaller than that of the former portion. The portions form partial planar sections having a slope gradually increasing towards the front side. An independent claim is also included for a traversing arrangement on an underneath construction.
