Pocket knife

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A pocket knife is a folding knife with a blade that fits inside the handle and that is small enough to fit in a pocket. Blades are typically no larger than 3 to 5 in. (8 to 13 cm) in length. Pocket knives are very versatile tools, and may be used for anything from opening an envelope, to cutting twine, to slicing an apple.

1 Slipjoint knives
2 Locking knives
3 Other features
4 Legal issues
5 See also
6 References

[edit] Slipjoint knives

Most pocket knives for light duty are slipjoints. This means that the blade does not lock, but, once opened, is held in place by a spring device that allows the blade to fold if a certain amount of pressure is applied.

These knives often have more than one blade, including an assortment of knife blade types (serrated, plain edged, saws) as well as a myriad of other tools such as bottle openers, corkscrews, and scissors. A large tool selection is the signature of the Swiss Army Knife. These knives are produced by Victorinox and Wenger and issued to the army and sold to the public. The German Army knife is large but light, with two blades opening from each side. It has hard plastic grips and aluminum liners. The United States Army knife, made by the Camillus Cutlery Company, used to have carbon steel blades and brass liners (both vulnerable to corrosion), but is now more durable with all-stainless steel construction. It has four blades opening from the same side. The handle, as manufactured, has rough edges, but these can be rounded, yielding an excellent and versatile knife.

Stockman's penknife with (from left to right) clip, sheep's foot and pen blades; wooden grips; brass bolsters and liners

Another method of non-locking knife is the friction-folder. These use simple friction between the blade and scales to hold the blade in place once opened.

Some popular styles of blade shapes are:

Clip — the upper part of the blade is cut away convexly to form a sharp point directly in front of the handle.
Spear — edge and back curve together to a point
Drop point — similar to spear but not necessarily symmetrical
Pen — similar to a spear but smaller
Sheep's foot — wide with straight edge and no point, common on boats and ships
Wharncliffe — flat cutting edge with back curve, similar to sheep's foot but with longer curve
Spay or spey — clipped at the back to form a sort of point, but the clip is very short. These were originally for castrating live stock and are used for delicate work.
Hook - The inside of the hook is sharp and the outside edge dull, so that a rope or animal skin can be cut without cutting the surface that the knife travels along. These blades are used by hunters for gutting animals and by emergency rescue people for cutting seat belts without harming the wearer.

There are many traditional types of folding knives:

A pen knife is a small and often thin knife with one or two pen blades, that does not interfere with the appearance of dress clothes, when carried in a pocket. They were originally intended for making and sharpening quill pens but are versatile and have remained fairly common. Knives with three or four knife blades are also common. A whittler is slightly larger than a pen knife and has three blades. A stockman has a clip, a sheep's foot and a spay blade. They are usually middle-sized. A trapper is large, with a clip and a spay blade. Another traditional styles is the Sodbuster.

Newer multitools have gained popularity in recent years:

The Leathermans and similar combination tools now compete with multi-bladed knives, but most of these are rather large for carrying in a pocket. The "main blade" is typically a pair of pliers and there is typically one non-locking knife blade.

The credit card knife is a very thin knife that is the shape and size of a credit card. It is designed to be carried in the wallet along with regular credit cards. Some of this shape of knife also contain other small tools, such as tweezers, or toothpicks.

[edit] Locking knives

Medium-sized lockback knife with deer-antler grips, nickel-silver bolsters and brass liners

The 1900s brought a new system to the knife world with the popularization of locking pocket knives. Companies such as Buck Knives, Benchmade, Camillus, Case, Gerber, Kershaw, Leatherman, Spyderco, and Opinel, to name a few, have created a wide range of products with locks of all types. The most popular form, the lockback knife (or buck knife) is a refinement of the slipjoint, where the spring along the back of the knife has a hook on it and the blade has a notch. When the blade is fully open the hook and notch align, locking the blade in place. Closing the blade requires the user releasing the blade to apply pressure to the back of the blade and in addition press on a lever located on the back of the knife handle to disengage the hook from the notch and thus release the blade. This locking mechanism adds a level of safety while cutting by preventing accidental closure. There are other types of locks; some of the more popular ones are the Walker Linerlock, the frame lock, where the bolster inside the knife is spring loaded to enagage the blade when open and thus hold it in place, and the Axis lock (a Benchmade patent). Even the Swiss Army knife product range has adopted the locks on their 111mm models. Leatherman and SOG tools are now available with locking blades.

Most slipjoint locking knives have only one blade that is as large as can be fit in the handle, because the locking mechanism relies on the spring along the back of the blade to lock it and it is difficult to have multiple levers for each blade. An electrician's knife typically has a locking screwdriver blade but a non-locking knife blade.

[edit] Other features

Traditional knives were opened using nail-nicks, or slots where the user's fingernail would enter to pull the blade out of the handle. This became somewhat cumbersome and required use of two hands, so there were innovations to remedy that. The thumb-stud, a small stud on the blade that allows for one-handed opening, led the way for yet more innovations, such as the opening hole (a Spyderco patent where the user presses the pad of his thumb against a hole and opens the blade by rotating his thumb similarly to using the thumb-stud), "assisted opening" systems pioneered by Ken Onion and his "Speed-Safe" mechanism, as well as Ernest Emerson's Wave system, where a hook catches the user's pocket upon removal and the blade is opened during a draw. One of the first one handed devices was the automatic spring release, also known as a switchblade.

Another innovation of Sal Glesser, Spyderco founder, was the clip system, which he named a "Clip-it". Clips are usually metal or plastic and similar to the clips found on pens except thicker. Clips allow the knife to be easily accessible, while keeping it lint-free and unscathed by pocket items such as coins.

[edit] Legal issues

Main article: Knife legislation

Nearly all pocket knives are legal to own in most countries, but they increasingly face legal restrictions on their use. While pocket knives are almost always used as tools, they do have the potential to become weapons. In many places it is illegal to conceal knives larger than a certain size, or with certain locking or opening mechanisms. They are often banned or heavily restricted in secure areas, such as schools and airports. Switchblades and other "auto-openers" are banned from interstate shipment by the U.S. Government and prohibited entirely in many places, including 37 U.S. states, though nearly all statutes prohibiting switchblades allow an exception permitting ownership by the one-handed, the military and the police. It is illegal to carry knives of any type in the UK, without good reason, except for folding knives with a cutting edge of 3 inches or less^[1]. Folding knives with blades of 3 inches or less may be carried so long as the blade is not capable of being opened automatically (either by gravity or mechanism e.g. flick and gravity knives), although a person behaving aggressively and in possession of any knife is likely to be in greater trouble.