Vise-grips, locking pliers, are one of the cleverest things I've seen. I've used them for all sorts of stuff, from making chainmail to destroying a VCR. I've even seen them used to make dunk tanks. Basically, they are a pair of pliers that can lock shut, with quite a bit of force, to adjustable sizes. To lock, you adjust the adjustment screw to about the size of what you want to be squeezing, and you close the jaws on it. Too release the lock, you press a little tab on the inside of the other handle, Sometimes, when grabbing something to hard, you need another pair of pliers just to open the Vise-Grip.

Now, I'm going to engage in what might be a fruitless effort to explain how a Vise-Grip works, with out the aid of and sort of diagram (Look Ma! No ASCII!):

The basic idea is that the swiveling side goes under the edge of the jaw, which means that the force in the jaws push the handles closer together. The adjustment screw adjusts how far out the swiveling jaw goes. The release lever, pushes the swiveling handle away from the swiveling jaw enough to allow the force of the thing in the jaws to open the grips, perhaps with a little help from the spring. But really, you gotta see it to understand it.

This is something that really should be in everyones tool box.

Vise-Grip is a trademark of American Tool.