Locking pliers are pliers which are designed to be locked closed, holding an object firmly without the need for the grip of a human hand. There are a number of different styles of locking pliers designed for various applications, and this product is readily available from many hardware stores. It is also possible to special order a set of pliers from a manufacturer or specialty company for a particular purpose.
As a general rule, no matter what the brand, these pliers typically have a screw which is used to adjust the pliers to the desired width apart, and a release handle which can be used to force the pliers open when they are no longer needed. When the pliers are locked down, they will hold onto the object without requiring the operator to grip the handles. This can be tremendously useful for all sorts of applications.