Abstract: The clamp mounts a cable and service lines in spaced relationship to a tubing string used in producing a well, and formed of lengths of tubing joined by a coupling. The clamp comprises first and second clamping elements for clamping around the tubing string and hinged on a first pin. A cover is hinged to the first element by a second pin. The first element and the inner surface of the cover are provided with formations which ensure that the cable and service lines are firmly held when the cover is closed against the first element by a captive bolt, which also clamps the first and second elements firmly around the coupling. A single hinge pin version clamps to the tubing string on each side of a coupling.