What are these clamps called? I have heard them called Marconi Clamps, etc. They are the clamps that hold the cable to a pole or building. They have a U shaped piece of steel to go through the eye bolt, and a hole in which to insert the cable messenger. The hole for the messenger has directional spikes that prevent the messenger from slipping back out of the clamp. To adjust the tension, you slide the messenger through the clamp until you reach the desired tension. You cut off the excess messenger with bolt cutters. Do these clamps have a universal name, or part number? Who do you get them from?