An OTF Knife, also known as an out-the-front knife, sliding knife, or telescoping knife, is a pocketknife with a blade that opens and closes through a hole in one end of the handle. Contrast this with the majority of knives, which are either standard folding knives or are "fixed blade" sheath knives (having no mechanical operation).

"OTF" only refers to the basic portion of the knife's mechanical operation where the blade slides parallel with the handle to deploy.

OTF knives may be further subdivided into manual sliding knives, which are not restricted as inertia knives, and automatic OTF switchblade knives and gravity knives, which are restricted offensive weapons.[1]

Switchblade

Switchblade

A switchblade is a type of knife with a folding or sliding blade contained in the handle which is opened automatically by a spring when a button, lever, or switch on the handle or bolster is activated A switchblade (also known as an automatic knife, pushbutton knife, switch, Sprenger, Springer,...

s and gravity knives

Gravity knife

A gravity knife is a knife with a blade contained in its handle, and which opens its blade by the force of inertia or gravity. As the gravity knife requires gravity or inertia to propel the blade out of the handle, it differs fundamentally from the switchblade, which opens its spring-propelled...

 provide a great variety of different OTF mechanisms.

"Gentlemen's" OTF knives

Illustrated above are four very small OTF knives. Figure A shows simple rocking jaw type button, and Figure B is a roll-lock design. Both figures depict gravity knives that fall open. The leading edge of the roll cap or jaw acts as a hole cover when closed, and rests in a groove milled across the open blade tang in order to lock open.

Figures C and D are known as sliders or sliding knives. The knife blade must be pushed with the button along the length of the handle, finger pressure must overcome friction. The lock buttons on C & D are not automatic releases. Figure C is a Christy Cutter (trademark) and Figure D is an antique design. The simplicity of sliding mechanisms have allowed some knife manufacturers to build extremely thin gentlemen's models, that are very comfortable to pocket.

Automatic OTF knives

An automatic OTF knife blade travels within an internal track or channel in the same manner as a manual slider or gravity knife. But the automatic main spring drive and button mechanism enclosed within requires a switchblade handle to be thicker or longer than a similar size gravity or sliding knife. The term "Slider" is usually not applied

There are two types of "Out the Front" automatic knives, DA-OTF (double-action) and SA-OTF (single-action). Double-action OTF knives deploy and retract with a multifunction button and spring design. Single-action OTF knives deploy automatically, but must be manually cocked or retracted to close.

Despite popular belief and movie magic, OTF automatic knives are not powerful enough to open when pressed against an opponent and then pushing the button. Double-action sliding autos are only spring-powered 10 to 12 millimeters; afterwards, kinetic impetus slides the blade to full open. Single-action OTF autos have a spring drive the full length of blade travel, but the size of the contained main spring is never large enough to drive a blade through much resistance. This is possibly a misbelief based on confusion with the ballistic knife

Ballistic knife

A ballistic knife is 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.-History and usage:...

 which has a secondary handle tube with a robust coil spring for launching a fixed blade knife.

Gravity OTF knives

A gravity OTF knife is also not considered a slider, because the blade extends outward by force of gravity or inertia, instead of finger pressure. The most famous gravity knife is the Fallschirmjaeger-Messer, or German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 paratrooper knife of World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The term gravity knife should primarily reference the Fallschirmjaeger-Messer as the archetypical example.

Spring-assisted gravity knives

Some civilian gravity OTF knives have a small helper spring to kick out the blade. This partial spring drive is not sufficient to classify this type of knife as a switchblade, because it does not drive the blade out to full lock.

Sheath-deployed telescoping knives

Another type of telescoping sliding knife is the Kershaw

Kershaw

Kershaw as a surname derives from a topographical identifier in the northern dialect of Middle English: kirk "church" and shaw "grove". Places named Kirkshaw include Kirkshaw in the parish of Rochdale, Lancashire, and two hamlets in West Yorkshire.-People:* Abbey Lee Kershaw , Australian fashion...

 Ripcord. This is a sheath knife that partially retacts into the handle, and has a small scabbard cap covering the remaining blade tip. The design utilizes a specialized belt hanger/holsters that grasps the retracted blade so the blade is pulled fully open when unholstering. It is a unique compact fixed blade alternative. During the 1990s, a similar sheath-activated sliding knife with embossed Red Star

Red star

A red star, five-pointed and filled, is an important ideological and religious symbol which has been used for various purposes, such as: state emblems, flags, monuments, ornaments, and logos.- Symbol of communism :...

 handle was sold in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, claimed to be a police

Police

The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...

 knife from the People's Republic of China

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

. However, no proof of this assertion has been shown.

Roll-lock sliding knives

A roll-lock knife is a type of sliding knife in which the blade rides on a track running the length of the scales, tilting into a detent to lock open or closed. Examples would be the Bench Mark Rollox, or its licensed derivative, the CRKT Rollock. Sliding knives like the Rollox are not considered inertia or gravity knife.

Spring-assisted out-the-front knives

Schrade and Smith & Wesson have both recently introduced OTF knives that are opened by sliding forward a handle attached to the blade to engage the torsion spring. As it is classified as spring-assisted, it is not covered by the Switchblade Act of 1958 and is therefore legal everywhere in the U.S.