A knife (plural knives) is a cutting tool with an exposed cutting edge or blade, hand-held or otherwise, with or without a handle. Knife-like tools were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. Originally made of rock, bone, flint, and obsidian, knives have evolved in construction as technology has, with blades being made from bronze, copper, iron, steel, ceramics, and titanium. Many cultures have their unique version of the knife. Due to its role as humankind's first tool, certain cultures have attached spiritual and religious significance to the knife.
Most modern-day knives follow either a fixed-blade or a folding construction style, with blade patterns and styles as varied as their makers and countries of origin.
Materials, features, and construction 
Today, knives come in many forms but can be generally categorized between two broad types: fixed blade and folding blade knives.
Parts of a knife 
A modern knife consists of
(1) a blade and
(2) a handle
The blade edge can be plain or serrated or a combination of both.
The handle, used to grip and manipulate the blade safely, may include the tang, a portion of the blade that extends into the handle. Knives are made with partial tangs (extending part way into the handle, known as a "Stick Tang") or full tangs (extending the full length of the handle, often visible on top and bottom). The handle can include a bolster, which is a piece of material used to balance the knife, usually brass or other metal, at the front of the handle where it meets the blade.
The blade consists of
(3) the point – the end of the knife used for piercing; (4) the edge – the cutting surface of the knife extending from the point to the heel;
(5), the grind, the cross section shape of the blade;
(6) the spine – the thickest section of the blade;
(7), the fuller, the groove added to lighten the blade;
(8) the ricasso, the flat section of the blade located at the junction of the blade and the knife's bolster or guard;
(9) the guard, the barrier between the blade and the handle which prevents the hand from slipping forward onto the blade
(10) the end of the handle, or butt. A choil, where the blade is unsharpened and possibly indented as it meets the handle, may be used to prevent scratches to the handle when sharpening or as a forward-finger grip. The knife's handle or butt may allow a
(11) lanyard to be used to secure the knife to the wrist, or a portion of the tang to protrude as a striking surface for hitting or glass breaking. Single edged knives may utilize a reverse edge or false edge, in which the forward section of the knife's spine (opposing the sharpened edge) is thinned and left unsharpened.
Knife blades can be manufactured from a variety of materials, each of which has advantages and disadvantages. Carbon steel, an alloy of iron and carbon, can be very sharp, hold its edge well, and remain easy to sharpen, but is vulnerable to rust and stains. Stainless steel is an alloy of iron, chromium, possibly nickel, and molybdenum, with only a small amount of carbon. It is not able to take quite as sharp an edge as carbon steel, but is highly resistant to corrosion. High carbon stainless steel is stainless steel with a higher amount of carbon, intended to incorporate the better attributes of carbon steel and stainless steel. High carbon stainless steel blades do not discolor or stain, and maintain a sharp edge. Laminate blades use multiple metals to create a layered sandwich, combining the attributes of both. For example, a harder, more brittle steel may be sandwiched between an outer layer of softer, tougher, stainless steel to reduce vulnerability to corrosion. In this case, however, the part most affected by corrosion, the edge, is still vulnerable. Pattern-welding is similar to laminate construction. Layers of different steel types are welded together, but then the stock is manipulated to create patterns in the steel. Titanium is a metal that has a better strength-to-weight ratio, is more wear resistant, and more flexible than steel. Although less hard and unable to take as sharp an edge, carbides in the titanium alloy allow them to be heat-treated to a sufficient hardness. Ceramic blades are hard, brittle, and lightweight: they may maintain a sharp edge for years with no maintenance at all, but are as fragile as glass and will break if dropped on a hard surface. They are immune to common corrosion, and can only be sharpened on silicon carbide sandpaper and some grinding wheels. Plastic blades are not especially sharp and typically serrated. They are often disposable.
Steel blades are commonly shaped by forging or stock removal. Forged blades are made by heating a single piece of steel, then shaping the metal while hot using a hammer or press. Stock removal blades are shaped by grinding and removing metal. With both methods, after shaping, the steel must be heat treated. This involves heating the steel above its critical point, then quenching the blade to harden it. After hardening, the blade is tempered to remove stresses and make the blade tougher. Mass manufactured kitchen cutlery uses both the forging and stock removal processes. Forging tends to be reserved for manufacturers' more expensive product lines, and can often be distinguished from stock removal product lines by the presence of an integral bolster, though integral bolsters can be crafted through either shaping method.
Knives are sharpened in various ways. Flat ground blades have a profile that tapers from the thick spine to the sharp edge in a straight or convex line. Seen in cross section, the blade would form a long, thin triangle, or where the taper does not extend to the back of the blade, a long thin rectangle with one peaked side. Hollow ground blades have concave, beveled edges. The resulting blade has a thinner edge, so it may have better cutting ability for shallow cuts, but it is lighter and less durable than flat ground blades and will tend to bind in deep cuts. Serrated blade knives have a wavy, scalloped or saw-like blade. Serrated blades are more well suited for tasks that require aggressive 'sawing' motions, whereas plain edge blades are better suited for tasks that require push-through cuts (e.g., shaving, chopping, slicing).
Fixed blade features 
A fixed blade knife, sometimes called a sheath knife, does not fold or slide, and is typically stronger due to the tang, the extension of the blade into the handle, and lack of moving parts.
Folding blade features 
A folding knife connects the blade to the handle through a pivot, allowing the blade to fold into the handle. To prevent injury to the knife user through the blade accidentally closing on the user's hand, folding knives typically have a locking mechanism. Different locking mechanisms are favored by various individuals for reasons such as perceived strength (lock safety), legality, and ease of use. Popular locking mechanisms include:
- Slip joint – Found most commonly on traditional pocket knives, the opened blade does not lock, but is held in place by a spring device that allows the blade to fold if a certain amount of pressure is applied.
- Lockback – Also known as the spine lock, the lockback includes a pivoted latch affixed to a spring, and can be disengaged only by pressing the latch down to release the blade.
- Liner Lock – Invented by Michael Walker, uses a leaf spring-type liner within the groove of the handle that snaps into position under the blade when it is deployed. The lock is released by pushing the liner to the side, to allow the blade to return to its groove set into the handle.
- Compression Lock – A variant of the Liner Lock, it uses a small piece of metal at the tip of the lock to lock into a small corresponding impression in the blade. This creates a lock that doesn't disengage when the blade is torqued, instead becoming more tightly locked. It is released by pressing the tab of metal to the side, to allow the blade to be placed into its grove set into the handle.
- Frame Lock – Also known as the integral lock or monolock, this locking mechanism was invented by custom knifemaker Chris Reeve for the Sebenza as an update to the liner lock. The frame lock works in a manner similar to the liner lock but uses a partial cutout of the actual knife handle, rather than a separate liner inside the handle to hold the blade in place.
- Collar lock – found on Opinel knives
- Button Lock – Found mainly on automatic knives, this type of lock uses a small push-button to open and release the knife.
- Axis Lock – A locking mechanism exclusively licensed to the Benchmade Knife Company. A cylindrical bearing is tensioned such that it will jump between the knife blade and some feature of the handle to lock the blade open.
- Arc Lock – A locking mechanism exclusively licensed to SOG Specialty Knives. It differs from an axis lock in that the cylindrical bearing is tensioned by a rotary spring rather than an axial spring.
- Ball Bearing Lock – A locking mechanism exclusively licensed to Spyderco. This lock is conceptually similar to the axis and arc locks but the bearing is instead a ball bearing.
- Tri-Ad Lock – A locking mechanism exclusively licensed to Cold Steel. It is similar to a lockback, but has a steel stop pin mounted between the front of the latch and the back of the blade for added strength.
- PickLock – A round post on the back base of the blade locks into a hole in a spring tab in the handle. To close, manually lift (pick) the spring tab (lock) off the blade post with your fingers, or in "Italian Style Stilettos" swivel the bolster (hand guard) clockwise to lift the spring tab off the blade post.
Another prominent feature on many folding knives is the opening mechanism. Traditional pocket knives and Swiss Army Knives commonly employ the nail nick, while modern folding knives more often use a stud, hole, disk, or flipper located on the blade, all which have the benefit of allowing the user to open the knife with one hand. The wave feature is another prominent design, which uses a part of the blade that protrudes outward to catch on one's pocket as it is drawn, thus opening the blade; this was patented by Ernest Emerson and is not only used on many of the Emerson knives, but also on knives produced by Spyderco and Cold Steel as well.
Automatic or switchblade knives open using the stored energy from a spring that is released when the user presses a button or lever or other actuator built into the handle of the knife. Automatic knives are severely restricted by law in most American states.
Increasingly common are assisted opening knives which use springs to propel the blade once the user has moved it past a certain angle. These differ from automatic or switchblade knives in that the blade is not released by means of a button or catch on the handle; rather, the blade itself is the actuator. Most assisted openers use flippers as their opening mechanism. Assisted opening knives can be as fast or faster than automatic knives to deploy.
Sliding blade features 
A sliding knife is a knife which can be opened by sliding the knife blade out the front of the handle. One method of opening is where the blade exits out the front of the handle point-first and then is locked into place (an example of this is the gravity knife). Another form is an O-T-F (out-the-front) switchblade, which only requires the push of a button or spring to cause the blade to slide out of the handle, and lock into place. To retract the blade back into the handle, a release lever or button, usually the same control as to open, is pressed. A very common form of sliding knife is the sliding utility knife (commonly known as a stanley knife or boxcutter).
The handles of knives can be made from a number of different materials, each of which has advantages and disadvantages. Handles are produced in a wide variety of shapes and styles. Handles are often textured to enhance grip.
- Wood handles provide good grip and are warm in the hand, but are more difficult to care for. They do not resist water well, and will crack or warp with prolonged exposure to water. Modern stabilized and laminated woods have largely overcome these problems. Many beautiful and exotic hardwoods are employed in the manufacture of custom and some production knives. In some countries it is now forbidden for commercial butchers' knives to have wood handles, for sanitary reasons.
- Plastic handles are more easily cared for than wooden handles, but can be slippery and become brittle over time.
- Injection molded handles made from higher grade plastics are composed of Polyphthalamide, and when marketed under trademarked names such as Zytel or Grivory, are reinforced with Kevlar or fiberglass. These are often used by major knife manufacturers.
- Rubber handles such as Kraton or Resiprene-C are generally preferred over plastic due to their durable and cushioning nature.
- Micarta is a popular handle material on user knives due to its toughness and stability. Micarta is nearly impervious to water, is grippy when wet, and is an excellent insulator. Micarta has come to refer to any fibrous material cast in resin. There are many varieties of micarta available. One very popular version is a fiberglass impregnated resin called G-10.
- Leather handles are seen on some hunting and military knives, notably the KA-BAR. Leather handles are typically produced by stacking leather washers, or less commonly, as a sleeve surrounding another handle material.
- Skeleton handles refers to the practice of using the tang itself as the handle, usually with sections of material removed to reduce weight. Skeleton handled knives are often wrapped with parachute cord or other wrapping materials to enhance grip.
- Stainless steel and Aluminum handles are durable and sanitary, but can be slippery. To counter this, premium knife makers make handles with ridges, bumps, or indentations to provide extra grip. Another problem with knives that have metal handles is that, since metal is an excellent heat-conductor, these knives can be very uncomfortable, and even painful or dangerous, when handled without gloves or other protective handwear in (very) cold climates.
More exotic materials usually only seen on art or ceremonial knives include: Stone, bone, mammoth tooth, mammoth ivory, oosik (walrus penis bone), walrus tusk, antler (often called stag in a knife context), sheep horn, buffalo horn, teeth, mop (mother of pearl or "pearl") etc. Many materials have been employed in knife handles.
Handles may be adapted to accommodate the needs of people with disabilities. For example, knife handles may be made thicker or with more cushioning for people with arthritis in their hands. A non-slip handle accommodates people with palmar hyperhidrosis.
Types of knives 
Knives as weapons 
As a weapon, the knife is universally adopted as an essential tool. It is the essential element of a knife fight. For example:
- Ballistic knife: A specialized combat knife with a detachable gas- or spring-propelled blade that can be fired to a distance of several feet or meters by pressing a trigger or switch on the handle.
- Bayonet: A knife-shaped close-quarters fighting weapon designed to attach to the muzzle of a rifle or similar weapon.
- Combat knife: Any knife intended to be used by soldiers in the field, as a general-use tool, but also for fighting.
- Dagger: A double-edged combat knife with a central spine and edges sharpened their full length, used primarily for stabbing. Variations include the Stiletto and Push dagger. See List of daggers for a more detailed list.
- Fighting knife: A knife with a blade designed to inflict a lethal injury in a physical confrontation between two or more individuals at very short range (grappling distance). Well known examples include the Bowie knife and the Fairbairn-Sykes Fighting Knife.
- Rampuri: An Indian gravity knife of formidable reputation having a single edged blade roughly 9 to 12 inches long.
- Shiv: A crudely made homemade knife out of everyday materials, especially prevalent in prisons among inmates. An alternate name in some prisons is Shank.
- Trench knife: Purpose-made or improvised knives, intended for close-quarter fighting, particularly in trench warfare characterized by a d-shaped integral hand guard.
- Butterfly knife: A folding pocket knife also known as a "balisong" or "batangas" with two counter-rotating handles where the blade is concealed within grooves in the handles.
Knives as sports equipment 
- Throwing knife: A knife designed and weighted for throwing
Knives as utensils 
- Bread knife: A knife with a serrated blade for cutting bread
- Boning knife: A knife used for removing the bones of poultry, meat, and fish
- Carving knife: A knife for carving large cooked meats such as poultry, roasts, hams
- Chef's knife: Also known as a French knife, a cutting tool used in preparing food
- Cleaver: A large knife that varies in its shape but usually resembles a rectangular-bladed hatchet. It is used mostly for hacking through bones as a kitchen knife or butcher knife, and can also be used for crushing via its broad side, typically garlic.
- Butcher's Knife: A knife designed and used primarily for the butchering and/or dressing of animals.
- Electric knife: An electrical device consisting of two serrated blades that are clipped together, providing a sawing action when powered on
- Kitchen knife: Any knife, including the chef's knife, that is intended to be used in food preparation
- Oyster knife: Has a short, thick blade for prying open oyster shells
- Paring or Coring Knife: A knife with a small but sharp blade used for cutting out the cores from fruit.
- Rocker knife is a knife that cuts with a rocking motion, which is primarily used by people whose disabilities prevent them from using a fork and knife simultaneously.
- Table knife or Case knife: A piece of cutlery, either a butter knife, Steak knife, or both, that is part of a table setting, accompanying the fork and spoon
- Ulu: An Inuit woman's all-purpose knife
Knives as tools 
As a utility tool the knife can take many forms, including:
- Balisong: A folding knife also known as a "butterfly knife" or "batangas", with two handles counter-rotating around the tang such that, when closed, the blade is hidden within the handles.
- Bowie knife: Commonly, any large sheath knife, or a specific style of large knife popularized by Jim Bowie.
- Crooked knife:sometimes referred to as a "curved knife", "carving knife" or in the Algonquian language the "mocotaugan" is a utilitarian knife used for carving.
- Diver's knife: A knife adapted for use in diving and water sports and a necessary part of standard diving dress.
- Electrician's knife: A short-bladed knife used to cut electrical insulation.
- Hunting knife: A knife used to dress large game.
- Linoleum knife: is a small knife that has a short, stiff blade with a curved point and a handle and is used to cut linoleum or other sheet materials.
- Machete: A large heavy knife used to cut through thick vegetation such as sugar cane or jungle undergrowth; it may be used as an offensive weapon.
- Palette knife: A knife, or frosting spatula, lacking a cutting edge, used by artists for tasks such as mixing and applying paint and in cooking for spreading icing.
- Paper knife: Or a "Letter Opener" it is a knife made of metal or plastic, used for opening mail.
- Pocket knife: a folding knife designed to be carried in a pants pocket. Subtypes include:
- *Produce knife: A knife with a rectangular profile and a blunt front edge used by grocers to cut produce.
- Scalpel: A medical knife, used to perform surgery.
- Straight razor: A reusable knife blade used for shaving hair.
- Survival knife: A sturdy knife, sometimes with a hollow handle filled with survival equipment.
- Switchblade: A knife with a folding blade that springs out of the grip when a button or lever on the grip is pressed.
- Utility knife: A short knife with a replaceable triangular blade, used for cutting sheet materials including card stock, paperboard, and corrugated fiberboard
- Wood carving knife and whittling knives: Knives used to shape wood in the arts of wood carving and whittling, often with short, thin replaceable blades for better control.
- X-Acto knife: A scalpel-like knife with a long handle and a replaceable pointed blade, used for precise, clean cutting in arts and crafts
Knives as a traditional or religious implement 
- Athame: A typically black-handled and double-edged ritual knife used in Wicca and other derivative forms of Neopagan witchcraft. (see also Boline).
- Kirpan: A ceremonial knife that all baptised Sikhs must wear as one of the five visible symbols of the Sikh faith (Kakars)
- Kilaya: A dagger used in Tibetan Buddhism
- Kris: A dagger used in Indo-Malay cultures, often by royalty and sometimes in religious rituals.
- Kukri: A Nepalese knife used as both tool and weapon
- Puukko: A traditional Finnish or Scandinavian style woodcraft belt-knife used as a tool rather than a weapon
- Seax: A Germanic single-edged knife, used primarily as a tool, but may have been a weapon
- Sgian Dubh: A small dagger traditionally worn with highland dress (kilt)
Rituals and superstitions 
The knife plays a significant role in some cultures through ritual and superstition, as the knife was an essential tool for survival since early man. Knife symbols can be found in various cultures to symbolize all stages of life; for example, a knife placed under the bed while giving birth is said to ease the pain, or, stuck into the headboard of a cradle, to protect the baby; knives were included in some Anglo-Saxon burial rites, so the dead would not be defenseless in the next world. The knife plays an important role in some initiation rites, and many cultures perform rituals with a variety of knives, including the ceremonial sacrifices of animals. Samurai warriors, as part of bushido, could perform ritual suicide, or seppuku, with a tantō, a common Japanese knife. An athame, a ceremonial black-handled knife, is used in Wicca and derived forms of neopagan witchcraft.
In Greece a black-handled knife placed under the pillow is used to keep away nightmares. As early as 1646 reference is made to a superstition of laying a knife across another piece of cutlery being a sign of witchcraft. A common belief is that if a knife is given as a gift, the relationship of the giver and recipient will be severed. Something such as a small coin, dove or a valuable item is exchanged for the gift, rendering "payment."
Knives are typically restricted by law, although restrictions vary greatly by country or state and type of knife. For example, some laws restrict carrying knives in public while other laws restrict private ownership of certain knives, such as switchblades.
Further reading 
- Everybody's Knife Bible by Don Paul, ISBN 0-938263-23-4
See also 
- "No. 1 The knife- Forbes.com". 2005-08-31. Retrieved 2007-05-07.
- "Early Human Evolution: Early Human Culture". Retrieved 2007-05-07.
- Kertzman, Joe (2007). Art of the Knife. Iola, WI: Krause Publications. pp. 3–6. ISBN 978-0-89689-470-9.
- "Knife Anatomy, Parts, Names". Retrieved 2007-05-07.
- "Greatest Tool #10: The Knife - lifehack.org". Retrieved 2007-05-07.
- State Knife Laws
- Braddom, Randall L.. Physical Medicine and Rehabilitation. Elsevier Health Sciences; 2010-12-07 [cited 28 April 2013]. ISBN 9781437735635. p. 568.
- "Bad Luck and Superstition 5". Retrieved 2007-05-08.
- "HouseholdFolklore". Retrieved 2007-05-08.
- ""The Knife Lore of the Anglo-Saxons" – Knife Articles : Custom Knives – Knife". Retrieved 2007-05-09.
- "The Heroic Age: The Anglo-British Cemetery at Bamburgh". Retrieved 2007-05-09.
- "Bronze age grave goods from Bedd Branwen burial site, Anglesey :: Gathering the Jewels". Retrieved 2007-05-09.
- "Ritual knife". Retrieved 2007-05-08.
- "Howstuffworks "How Samurai Work"". Retrieved 2007-05-08.
- "Hellenic Magical Ritual". Retrieved 2007-05-08.
- "The Clavicle of Solomon, revealed by Ptolomy the Grecian. (Sloane 3847)". Retrieved 2007-05-08.
- "The Magic of the Horseshoe: The Magic Of The Horse-shoe: VI. Iron As A Protective Charm". Retrieved 2007-05-08.
- "Knife laid across – A Dictionary of Superstitions – HighBeam Research". Retrieved 2007-05-08.
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