A coupling (or coupler) (used in piping or plumbing) is a very short length of pipe or tube, with a socket at one or both ends that allows two pipes or tubes to be joined, welded (steel), brazed or soldered (copper, brass etc.) together.
Earth clamps are used for bonding copper conductors onto steel surfaces – clamp is fixed by drilling a hole in the steelwork and securing with the set screw provide and Grounding Rod Fittings.
Coupler & Clamp