as can be seen in fig6 the clamping member is extended at one side by an outwardly jutting portion l and at its other side by an oppositely disposed normally bent off portion m this clamping or holding member is indicated generally by the reference numeral 15 a corner piece and its use is illustrated by fig5 each of the corner pieces comprise a triangular top plate n and two vertical triangular side plates o and p welded to the plate n to the plate n are furthermore welded two short plates q and r which extend in planes parallel to the triangular plates o and p at a distance therefrom two further plates s and t extend at a right angle from plates o and p in assembling first the skeleton which is intended to hold the wall panels the four profiled bars 1 2 3 and 4 are connected by the connecting members 9 shown in fig1 and fig5 this is simply done by inserting the profiled bars 1 4 into the space defined between the triangular plates o and q and p and r respectively obviously the distance between the triangular plates and small plates q and r is such that the bars 1 4 fit thereinto and in fact have to be forced into the space the bars 1 4 are held in the aforementioned spaces by friction and due to the springiness of the metallic parts of the connector 9 the so obtained rectangular or square frame is placed.