Connecting device with nut having right-hand and left-hand threading

The two pipe fittings (2,3) have flat mating faces (10,11) which are pressed together by turning the nut (4). Rods (9) fit into blind bores in the two fittings to prevent relative rotation. The first end of the nut and the first pipe fittings have right-hand threads (5,7) and the second end of the nut and the second pipe fitting have left-hand threads (6,8).