Hi all, I discovered a wonderful tool at Home Depot about a year ago. It's a special Vise-Grips pliers that has jaws shaped to grip a hex nut or bolt. The stationary jaw is kind of vee-shaped and the adjustable jaw is like a truncated pyramid. So you put the jaws around any frozen tubing nut in typical Vise-Grip fashion and loosen the nut. This tool has never failed me during all of my junkyard part-pulling outings. It doesn't matter if the tubing nut is already rounded off or otherwise butchered. This tool will win. Pete in PA