Yea... I've watched this video along with about a dozen others a few times over. I can watch most jobs and understand what's going on within a few minutes. When it comes to rigging though.... I'm not too sure. The clamps hold the drill pipe in place, there are two of them so they can rotate either way. The chains are attached to those clamps somehow and provide the rotation to screw the new pipe into the pipe that's hanging. Then it's hoisted up and spun onto the pipe that's clamped into the drill floor. I'd love to spend a day filming the operation of one of these things so I could see it all happen and finally understand. I was thinking about doing this shit at one point, but realized I made about as much money as they would, and couldn't see myself surviving that job for long.