one of the panels 2 through an opening 18 provided in the wall of the profiled elements 3 the angular rotation of the plates 15 16 is determined by the translatory motion of a shank 19 which slideably engages respective mutually oblique elongated slots 20 21 of said plates the shank 19 has a portion provided with a female thread 22 which is coupled to a threaded stem 23 and is movable within a seat 24 provided in the spacer block 4 the stem 23 is provided at one end with a diametral notch 25 accessible through the cavity 14 for the engagement of an appropriate tool thus by rotating the stem 23 the shank 19 can be displaced along the seat 24 and the plates 15 16 owing to the oblique slots 20 21 are caused to rotate in opposite directions thus pressing the panels 2 against the outer edge 6 of the profiled elements 3 as indicated in broken lines 2a in fig4 each pair of planar parallel panels 2 is thus positioned at its corners by means of respective devices 1 and rigidly associated by means of a pair of crossed tension members 5 which thus clamp when tensioned the pair of panels with a compressed action in a diagonal direction said pair of panels is intended to be connected in order to form a dividing wall to similar.