Variable Joint Pliers

Variable joint pliers are available in different styles 

Slip joint pliers have movable pivots, which can be adjusted down the length of the device to increase the distance that the jaws can open. Channel pliers are similar but use a sliding rather than pivoting mechanism to adjust the jaws.

Straight slip joint pliers have jaws in line with their handles, while tongue-and-groove - or ‘water pump’ - pliers have their jaws offset.The latter are most frequently used by plumbers, electricians and mechanics for adjusting nuts and bolts, as well as other fittings with an irregular shape. They typically have serrated jaws set at a 45 to 60 degree angle from the precisely aligned handles.

Water pump pliers have several alternative names, including arc joint pliers and pipe spanners.