I'm sure this has happened to you. You try to loosen or tighten a bolt like this with the head rounded off and you find that an adjustable wrench is practically useless. Well, this is where you need a locking jaw plier. These are adjustable with this knob back here. You want to turn this until the pliers really snap into place. But once it's there, it's like having a vice on the head of that bolt and you can turn it as much as you want to. But not all of these are created equal. This one which we used on the bolt has got a straight jaw. For curved things like this piece of pipe, you want to choose a locking plier that has a curved jaw.