Pocket knives are tools which can be folded to fit with the size of your pocket. With a much smaller size the tool contains multiple blades inside it with a length of ½ inch to 12 inches. There are some simple designs as well as a number of complex designs which can be used for performing tasks of entirely different nature. Some of the designs are used for slicing an apple, opening an envelope and even for a person's self defense. The history of these instruments goes back to the Iron Age which is even older than the history of pockets. However, one cannot use the term pocket knives for the ancient tools as pocket was attached to clothes during a much later period. People categorize these instruments based on various categories like multitool slipjoint knives, slipjoint knives, tactical folding knives, and locking knives. A number of jurisdictions have banned the usage of fixed-blade knives, whereas it is perfectly legal to carry these tools in other jurisdictions.
These instruments are a combination of various knife and other tool designs. Most of these instruments contain multiple blades with various assortments like, plain edged, saws, and serrated. Further, these knives contain other tools which serve different purposes like corkscrews, bottle openers, and scissors. The combination of different blades and these tools make this category of pocket knives very much popular. There are also a military version of these designs which were used commonly by the German and USA soldiers while participating in various wars. Also, there is a credit card knife which is tiny enough to be carried inside your wallet.
The lockback and clasp models of these knives are also considered as a specific category of instruments which you can carry inside your pocket. The knife has to be released using a separate action before being folded due to the twisting ring or catch mechanism used in these designs. In comparison to the slipjoint knives this category of pocket knives are much safer as these instruments are better designed to prevent accidental blade movement and closure while the device is being used for cutting and other functionalities.
This category of pocket instruments gained wide spread popularity during the 1990s due to the restrictions imposed by amended gun laws. There are specific makers who use liner locks in making these instruments whereas some other use axis locks. The earlier versions of these instruments were sporting blades with a length of 3 to 12 inches. But the legal restrictions imposed in some of the jurisdictions make these makers restrict the blade length to 4 inches. The huge demand for this category of pocket knives encouraged various companies to come up with their own version of these tactical folding knives.
You can buy and carry these instruments in your pocket as it is legal in most of the jurisdictions in the U.S.A. However, you cannot carry these tools a number of areas which are sensitive to various security threats. All schools and air ports impose restrictions on the usage of these knives within their coverage area.