u201d is used as well as for their usage at curved surfaces also the value of h 1 fig2 is important for the basewall structure the size h 1 defines height of the lateral lugs 9 and distance between the basewall lower surface 2 and horizontal surface 3 the lateral lugs 9 are necessary for the following when there is no lateral lug h 1 0 the basewall 1 lower surface 2 is plane fig2 as the recommended value of h is too small in a case of the basewall flat lower surface its significant part could come into contact with the surface 3 conditionally let 39 s name this part of contacting surfaces as area x fig1 when rotating the basewall in the area x some significant friction between the basewall 1 lower surface 2 and surface 3 is appeared in addition different foreign fine particles dust fine sand particles of food etc could be present at the surface 3 they also could resist to the basewall rotation significantly to exclude the above factors which resist to the basewall rotation the application of h 1 h and more is recommended as well as ratios of the above parameters for the first and second variants of the invention when manufacturing the basewall the maximum value of h 1 shall be defined whether based on esthetic considerations or technological requirements also the maximum value of h 1 could be defined based on more complicated shape of the lower surface 2 in the cases when such a shape of the lower surface leads to improving the basewall rotation based on esthetic considerations the basewall could have more complicated configuration the central lug 7 lateral lugs 9 and lower surface 2.