I just read the first page of reviews on Amazon. I've never had a problem with it gripping a smooth pipe like one or two of the reviews said. In fact, that's what I bought them for- to turn the shaft in the center of a roll-up door to adjust the tension. A helper and I would be on each end of the door and we'd use the wrenches to put 1/4 turns on the shaft, taking turns. I've hung from them biting onto the door shaft. This was back in '01-'06, though. I hope they didn't switch to crappier materials and/or build quality since then.