Pliers are hand tools designed for gripping or bending objects. Their design allows the worker to apply greater leverage than if the hands or fingers alone were used to grasp an object. Because the handles are longer than the jaws, the handles act as levers and are able to amplify the force applied to the object being gripped. Pliers can also include cutting features and a rubber or plastic coating on the handles to help the user get a good grip. The size of pliers varies; they can be 4 inches (about 10 cm) to some 20 inches (almost 51 cm) long.
The simple structure of a set of pliers consists of two handles, joined at the neck, fulcrum, or pivot point. At the other end of the pivot point is the opening of the pliers, which is referred to as the head, mouth, or jaws. The tool, developed more than 4,000 years ago in Europe, has been modified over the years for specialized uses.
Slip joint pliers are one type of plier. Unlike basic pliers, also called solid joint pliers, which are not adjustable, slip joint pliers can be adjusted to allow for different sized mouth openings. The pivot point of these pliers can be moved to adjust to the size of the object being gripped. A slot in the neck allows the pivot to slide between at least two, sometimes more, positions. The adjustable pivot point in slip joint pliers is usually one of two types of construction — either it will have two or more preset holes, or it will have a tongue and groove construction.
Straight slip joint pliers are probably the most common type of slip joint plier, especially in the United States. They feature jaws that are in line with the plier handles. There are multiple varieties of straight slip joint pliers including thin nose, thick nose, regular, and multiple slip joint pliers which allow more than two pivot positions.
The jaws of some pliers are set at a 45 to 60 degree angle in relation to the handles. The jaws of these pliers resemble the letter "C". Sometimes called water pump, or pipe pliers, this type of plier often has larger handles, generally to deal with the larger items they are used to grip.