A method for the realisation and the maintenance of overhead line plants for telecommunications, in which the anchor or 'mooring' device of the self-gripping two-way supports of the cables, is made integral with a movable structure free to move along the supporting post. The structure comprises a chain allowing to lower the line from span level to ground level, and its successive lifting to the predetermined operative height at the end of the maintenance intervention; said lowering of the line to the ground level being obtained by expoliting the gravity force acting on the line itself, and the successive lifting, by pulling this anchor chain. The movable structures are realised according to different configurations, depending on the characteristics of the posts where these structures are used.