bar 7 wherein the guide preferably is designed as dovetail guide defining a groove 16 the dovetail guide extends in the longitudinal direction of the flat bar 7 the dovetail guide forms one piece together with the flat bar 7 and consists of two guide rails 15 which respectively stop at a longitudinal edge on the top of flat bar 7 the heights of these guide rails 15 are adapted to the structural height of the base support 11 with clothing 8 positioned thereon in addition the spacing between the guide rails 15 is adapted to the width of the base support 11 with clothing 8 positioned thereon so that the base support 11 with clothing 8 fits tightly against the insides of the guide rails 15 the base support 11 with clothing 8 is inserted from the front or back end of flat bar 7 into the guide opening until the base support 11 with its total length rests on the top of flat bar 7 in order to secure the base support 11 on the flat bar 7 threaded bores that are not depicted here can be provided in the side walls of guide rails 15 and the base support 11 screws for fastening the base support 11 to the guide rails 15 are inserted into these threaded bores alternatively or in addition the base support 11 with clothing 8 that is positioned in the guides can be secured by closing off the end parts of the guides at the front and.