Procedure for the assembly of a held organ of for rotary trees, the comprising type an external ring (8) and an inner ring (10). The inner ring introduces a surface of held (20) on which capacity from the external ring acts labbro the 42 of a packing (14) (8). I1 procedure previews the insertion of the organ of estate (6) in a center (30) until to that the inner ring (10) enters in struck with a surface of arrest (48) that and contrasts an axial force on the inner ring (10) directed in the back of insertion of the estate organ (6). The procedure previews moreover an axial movement of the external ring (8) regarding the inner ring (10) so as to distance between they two radial portions pointed out (16, 18; 26) of the external ring (8) and the inner ring (10). (fig.1)