Water pump pliers (Channel-Locks).
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Tongue-and-groove pliers, also known as water pump pliers, adjustable pliers, groove-joint pliers, and Channellocks, are a type of slip-joint pliers. They have serrated jaws generally set 45– to 60-degrees from the handles. The lower jaw can be moved to a number of positions by sliding along a tracking section under the upper jaw. An advantage of this design is that the pliers can adjust to a number of sizes without the distance in the handle growing wider. These pliers often have long handles—commonly 9.5 to 12 inches long—for increased leverage.
Tongue-and-groove pliers are commonly used for turning and holding nuts and bolts, gripping irregularly shaped objects, and clamping materials.
This design of pliers was invented and popularized by the Champion–DeArment Tool Company in 1934 under the brand name Channellock (after which the company would eventually take its name) but are also now produced by a number of other manufacturers.