Locking pliers, mole grips (mole wrench) or vise-grips are pliers that can be locked into position, using an over-center action. One side of the handle includes a bolt that is used to adjust the spacing of the jaws, the other side of the handle (especially in larger models) often includes a lever to push the two sides of the handles apart to unlock the pliers. "Mole" and "Vise-Grip" are trade names of different brands of locking pliers.
Locking pliers are available in many different configurations, such as needle-nose locking pliers, locking wrenches, locking clamps and various shapes to fix metal parts for welding. They also come in many sizes.
Locking pliers Wikipedia
The jaws are set to a size slightly smaller than what is to be gripped by turning the bolt in one handle with the jaws closed. Some new versions have slots in the handle bolt which can be further tightened with a hex key or screw driver. When the jaws are opened and the handles squeezed together, they move a lever over its centre point and lock the jaw of the pliers onto the gripped object. A typical usage would be to hold metal parts in place for welding. They are also invaluable for holding a nut or bolt that has been 'rounded' or as temporary levers/knobs on equipment and machinery.
The first locking pliers, named Vise-Grips, were invented by William Petersen in De Witt, Nebraska in 1924. Mole grips were developed by Thomas Coughtrie (1917–2008) in 1955, then managing director of M. K. Mole and Son. Mole Grips were manufactured in Newport South Wales just off the M4 by the Brynglas Tunnels, travelling west the Mole sign was visible immediately before entering the tunnel.