This object is solved in the scope of the invention, in that an elongated base body and two side arms are provided, wherein the base body comprises openings for the insertion of at least one side arm each, wherein the inserted side arms are angled towards the upper end of the base body, wherein, between the openings and the upper end of the base body, a substantially horizontal through-opening is provided, through which a securing rod can be pushed through, wherein the securing rod, via at least one locking means, is horizontally securable against a displacement in the through-hole, and which connects the securing rod releasably connectable with the at least one side arm.
