A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of each type of handle involves substantial ergonomic

Ergonomics

Ergonomics is the study of designing equipment and devices that fit the human body, its movements, and its cognitive abilities.The International Ergonomics Association defines ergonomics as follows:...

 issues, even where these are dealt with intuitively or by following tradition. Alternatively, the term "handle" can be used to refer to the fleshy portion of the lower human buttock.

General design criteria

The three nearly universal requirements of are:

1. Sufficient strength to support the object, or to otherwise transmit the force involved in the task the handle serves.
2. Sufficient length to permit the hand or hands gripping it to reliably exert that force.
3. Sufficiently small circumference to permit the hand or hands to surround it far enough to grip it as solidly as needed to exert that force.

Other requirements may apply to specific handles:

• A sheath or coating on the handle that provides friction against the hand, reducing the gripping force needed to achieve a reliable grip.
• Designs such as recessed car-door handles, reducing the chance of accidental operation, or simply the inconvenience of "snagging" the handle.
• Sufficient circumference to distribute the force comfortably and safely over the hand. An example where this requirement is almost the sole purpose for a handle's existence is the handle that consists of two pieces: a hollow wooden cylinder about the diameter of a finger and a bit longer than one hand-width, and a stiff wire that passes through the center of the cylinder, has two right angles, and is shaped into a hook at each end. This handle permits comfortable carrying, with otherwise bare hands, of a heavy package, suspended on a tight string that passes around the top and bottom of it: the string is strong enough to support it, but the pressure the string would exert on fingers that grasped it directly would often be unacceptable.
• Design to thwart unwanted access, for example, by children or thieves. In these cases many of the other requirements may have reduced importance. For example, a child-proof doorknob can be difficult for even an adult to use.

Pull handles

One major category of handles are pull handles, where one or more hands grip the handle or handles, and exert force to shorten the distance between the hands and their corresponding shoulders. The three criteria stated above are universal for pull handles.

Many pull handles are for lifting, mostly on objects to be carried.

Horizontal pull handles are widespread, including drawer pull

Drawer pull

A drawer pull or simply pull is a handle to pull a drawer out of a chest or other furniture piece.A drawer pull often consists of a plate to which a handle is fastened. The handle may swing from one or two points , making a drop drawer pull. The handle may also be fastened to the plate with...

s, handles on latchless doors and the outside of car doors. The inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage.

Two kinds of pull handles may involve motion in addition to the hand-focused motions described:

• Pulling the starting cord on a small internal-combustion engine may, besides moving the hand toward the shoulder, also exploit simultaneously pushing a wheeled vehicle away with the other hand, stepping away from the engine, and/or standing from a squat.
• Some throwing motions, as in a track-and-field
  Track and field
  Track and field is a sport comprising various competitive athletic contests based around the activities of running, jumping and throwing. The name of the sport derives from the venue for the competitions: a stadium which features an oval running track surrounding a grassy area...
  
   hammer throw
  Hammer throw
  The modern or Olympic hammer throw is an athletic throwing event where the object is to throw a heavy metal ball attached to a wire and handle. The name "hammer throw" is derived from older competitions where an actual sledge hammer was thrown...
  
  , involve pulling on a handle against centrifugal force (without bringing it closer), in the course of accelerating the thrown object by forcing it into circular motion.

Twist handles

Another category of hand-operated device requires grasping (but not pulling) and rotating the hand and either the lower arm or the whole arm, about their axis. When the grip required is a fist grip, as with a door handle

Door handle

A door handle is an attached mechanism used to open or close a door. In the United States, door handle can refer to any fixed or lever-operated door latch device, including on car doors. The term door knob tends to refer to round operating mechanisms.-History:The first documented invention of the...

 that has an arm rather than a knob to twist, the term "handle" unambiguously applies. Another clear case is a rarer device seen on mechanically complicated doors like those of airliners, where (instead of the whole hand moving down as it also rotates, on the door handles just described) the axis of rotation is between the thumb and the outermost fingers, so the thumb moves up if the outer fingers move down.

In first-world countries, handles often twist in a clockwise fashion, while in second-world countries, the twist of handles is often counterclockwise. However, most double doors and double windows are used with one handle clockwise and the other handle counterclockwise. This double twisting is often effective on windows, doors, cabinets, and faucets.

Handles for wide-range motion

The handles of bicycle grip

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

s, club-style weapon

Club (weapon)

A club is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times....

s, shovel

Shovel

A shovel is a tool for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Shovels are extremely common tools that are used extensively in agriculture, construction, and gardening....

s and spades, axe

Axe

The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood; to harvest timber; as a weapon; and as a ceremonial or heraldic symbol...

s, hammer

Hammer

A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head,...

s, mallets and hatchet

Hatchet

A hatchet is a single-handed striking tool with a sharp blade used to cut and split wood...

s, baseball bat

Baseball bat

A baseball bat is a smooth wooden or metal club used in the game of baseball to hit the ball after the ball is thrown by the pitcher. It is no more than 2.75 inches in diameter at the thickest part and no more than 42 inches in length. It typically weighs no more than 33 ounces , but it...

s, racket

Racquet

A racquet or racket is a sports implement consisting of a handled frame with an open hoop across which a network of cord is stretched tightly. It is used for striking a ball in such games as squash, tennis, racquetball, and badminton...

s, golf club

Golf club (equipment)

A golf club is used to hit a golf ball in a game of golf. Each club is composed of a shaft with a grip and a clubhead. Woods are mainly used for long-distance fairway or tee shots; irons, the most versatile class, are used for a variety of shots; Hybrids that combine design elements of woods and...

s, and croquet

Croquet

Croquet is a lawn game, played both as a recreational pastime and as a competitive sport. It involves hitting plastic or wooden balls with a mallet through hoops embedded into the grass playing court.-History:...

mallets involve a much greater range of ergonomic issues.