A gravity knife is a
knife
A knife (: knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least Stone Age, 2.5 million years ago, as e ...
with a blade contained in its handle, which opens its blade through the force of
gravity
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
.
This mechanism of opening is fundamentally different from the
switchblade
A switchblade (also known as switch knife, automatic knife, pushbutton knife, ejector knife, flick knife, gravity knife, flick blade, or spring knife) is a pocketknife with a sliding or pivoting blade contained in the handle which is extended ...
, which extends its spring-propelled blade automatically upon the push of a button, switch, or
fulcrum lever.
The main purpose of gravity opening is to allow opening and closing to be done with one hand, in situations where the other is occupied. Hence, historically,
parachutist
Parachuting and skydiving are methods of descending from a high point in an atmosphere to the ground or ocean surface with the aid of gravity, involving the control of speed during the descent using a parachute or multiple parachutes.
For hu ...
s have been issued them to cut off caught lines, such as lines tangled in trees, a major potential use of the gravity knife.
The gravity knife uses a button, trigger, or fulcrum lever to release the blade from both the open and the closed positions, and may use a side-folding or telescoping (out-the-front, or OTF) blade. While most military gravity knives utilize a locking blade design, other types may not mechanically lock open but rely instead upon friction to wedge the blade's rear section against the handle's interior.
Factory-made gravity knives have various types of buttons, triggers, and fulcrum levers, which usually are used to release the blade from both the open and the closed positions.
Design and operation
Flieger-Kappmesser / Luftwaffe Gravity Knife (LGK)

One of the most recognizable gravity knives is the
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
-era (), which utilizes a telescoping (OTF), gravity-propelled locking blade. First produced in 1937, the often so called () was initially issued to German flight crews and paratroops, primarily to cut a trapped parachutist from his rigging in case he landed with a tangled parachute, or became entangled in trees or in the water with the
shroud lines.
The
spike was used to untie knots while packing the parachutes. Luftwaffe air crew members used the knife to cut themselves out of their harnesses or cut through the aluminum hull of the aircraft after a crash landing. Though not intended for use as a fighting knife in the first place, the LGK was introduced to the
1st Skijäger Division and SS units on the
Eastern Front to be used primarily as a close combat weapon from 1944 on.
The uses a sliding blade inside a metal grip frame, which was initially fitted with smooth wood scales. The blade is relatively blunt
spear-point, and the profile is flat ground, tapering to a utility edge. To open the blade, the user points the knife downwards while flipping up the fulcrum-style operating lever, allowing gravity to draw out the blade to its fullest extent. Releasing the lever locks the blade into position. The LGK may also be opened by flipping the blade release lever while flicking the wrist holding the knife, causing the blade to extend. The LGK was also equipped with a folding
marlinspike
A marlinspike (, sometimes spelled marlin spike, marlinespike, or rchaicmarlingspike) is a tool used in marine ropework. Shaped in the form of a narrow metal cone tapered to a rounded or flattened point, it is used in tasks such as unlaying r ...
or
awl. Primarily intended for untangling rope knots, it was also used as a prying tool or to fix jammed weapons. The spike does not lock when opened and was never intended to be used as a combat weapon.
There are two principal types of wartime-era with 10 known variations. The Type I LGK (three manufacturers, five WWII variations) has wood scales (handle), was made from 1937 to 1943, and, unlike successive models, has no takedown capability. The Type II LGK (two manufacturers, five WWII variations) is the same knife, but with takedown features, and was produced from 1943 until 1945 and then again from c. 1950 until 1965.
After the end of World War II, the newly organized West German placed new orders with German cutlery manufacturers for a postwar version of the for issue to the Army's airborne forces and tank crews. The West German abandoned the gravity knife concept completely and purchased different rescue knives, including a shroud line cutter. The initial Type III "trap door" gravity knife, made from 1955 to 1961, was unreliable. Thus, the original WWII Type II design was reintroduced until the early Type IV knives finally replaced it in 1968. The Type IV LGK is similar to the WWII-production Type II takedown knife but features plastic polymer instead of wooden scales. It was made by WMF, OFW, and Eickhorn from 1972 to 1984. They were issued to soldiers until 2017. The third West German post-war model is the Type V LGK, initially named AES79 and still today produced under the designation LL80 (1979–present) by Eickhorn. The LL80 is smaller, has fewer parts, and is more cost-effective than earlier .
[Pattarozzi, Mack A. (2006), ''Luftwaffe Gravity Knife: A History And Analysis of the Flyer's And Paratrooper's Utility Knife'', Schiffer, . 'Takedown' refers to the knife's ability to quickly disassemble into its component parts without tools.] It was procured by the
Swiss Air Force
The Swiss Air Force (; ; ; ) is the air component of the Swiss Armed Forces, established on 31 July 1914, three days after the outbreak of World War I, as a part of the Swiss Army, army and in October 1936 as an independent service.
In peaceti ...
and issued to their
Dassault Mirage
Mirage is a name given to several types of jet aircraft designed by the French company Dassault Aviation (formerly Avions Marcel Dassault), some of which were produced in different variants. Most were supersonic fighters with delta wings. The most ...
pilots in 1983. These knives are marked AES83 and bear the number of the aircraft on the metal head.
On the other side of the
Iron Curtain
The Iron Curtain was the political and physical boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1991. On the east side of the Iron Curtain were countries connected to the So ...
, in the
German Democratic Republic
East Germany, officially known as the German Democratic Republic (GDR), was a country in Central Europe from Foundation of East Germany, its formation on 7 October 1949 until German reunification, its reunification with West Germany (FRG) on ...
, WWII gravity knives were refurbished and re-issued to the paratroopers and pilots until the existing stock was gone. In the early 1960s, two companies produced an East German version of the Type I knives. They were then used until the early 1970s.
Ibberson gravity knife
After British forces had captured numbers of Type I , the British government approached
George Ibberson & Co. of
Sheffield
Sheffield is a city in South Yorkshire, England, situated south of Leeds and east of Manchester. The city is the administrative centre of the City of Sheffield. It is historically part of the West Riding of Yorkshire and some of its so ...
, England, a knife and cutlery manufacturer, and requested production of a British version of the German Luftwaffe Gravity Knife for the
Special Operations Executive
Special Operations Executive (SOE) was a British organisation formed in 1940 to conduct espionage, sabotage and reconnaissance in German-occupied Europe and to aid local Resistance during World War II, resistance movements during World War II. ...
(SOE) and other clandestine warfare units.
[Ladd, James D.; Melton, Keith; and Mason, Peter (1988). ''Clandestine warfare: weapons and equipment of the SOE and OSS''. London: Blandford. . p. 29. These British SOE gravity knives are ''not'' the same as the standard British Army soldier's and sailor's clasp pocketknife, featuring a short, thick marlinspike.] Under the initial wartime contract, George Ibberson & Co. made 500 gravity knives for issue to the SOE and other special forces. These Sheffield gravity knives had smooth wood or textured plastic scales. Still, they were otherwise identical in features and operation to the Type I , with a locking gravity-deployed blade and a folding rigging spike or awl. In the hands of British SOE agents, the Sheffield gravity knife was considered to be a secondary combat weapon. In addition to the knife blade, SOE close combat instructors found that the folding rigging spike was useful for silent killing of sentries by opening the carotid artery on the neck.
'False gravity' and non-gravity knives
Some folding or telescoping knives that can open their blades by force of inertia or gravity were not intended or advertised by the manufacturer to do so. Knives that will lock their blades open, but do not have any closed position lock device, are referred to as "false" gravity blades.

The illustration shows the internal parts of a 1960s Japanese import 'false' gravity knife. Other knives may be considered 'false' gravity knives, including certain lock-back and liner lock folding knives that will not lock a blade in both open and closed positions.
After the passage of the Switchblade Knife Act in the U.S. in 1958, it was discovered that some U.S. businesses were importing folding
stiletto
A stiletto (plural stilettos) is a specialized dagger with a long slender blade and needle-like point, primarily intended as a thrusting and stabbing weapon.Limburg, Peter R., ''What's In The Names Of Antique Weapons'', Coward, McCann & Geoghega ...
knives without spring mechanisms that did not have a pronounced blade heel (internal surface) in the pivot area allowing the longer bladed models to flick open quickly.
Modern (post 1965) folding stilettos imported or distributed in the U.S. now have blade heels that are intentionally pointed and ratchet against the lockback mechanism, preventing inertia opening.
Other knives commonly mistaken for gravity knives include the automatic
OTF knife
An OTF Knife, also known as an out-the-front knife, sliding knife, telescoping knife, or angel blade, is a pocketknife with a blade that opens and closes through a hole in one end of the handle. This design contrasts with the majority of utilit ...
, the
switchblade
A switchblade (also known as switch knife, automatic knife, pushbutton knife, ejector knife, flick knife, gravity knife, flick blade, or spring knife) is a pocketknife with a sliding or pivoting blade contained in the handle which is extended ...
and the
butterfly knives (or balisong), the
sliding knife,
penny knife, and occasionally even common folding hunting knives such as the Buck 110 Folding Hunter.
Other
The 'conversion' gravity knife is a standard folding knife fitted with after-market modifications.
The knife pictured does not lock closed, and is thus classed as a 'false' gravity knife. It can still be opened manually without touching the toggle switch. The addition of the toggle, which is attached to an internal bellcrank-arm, will lift the lockback mechanism to allow the blade to swing more easily.
Legality
In some countries, such as the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
,
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, and some
U.S. state
In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...
s, a gravity knife is proscribed under the law as a prohibited weapon, with attendant criminal penalties. Other laws may criminalize the ownership, sale, importation, or carrying of a gravity knife upon one's person, either concealed or unconcealed. In the United States, some state criminal codes prohibit either the ownership or the carrying of gravity knives, either by name or by including a functional description of their opening mechanisms. Other state criminal codes bar gravity knives by redefining them variously as switchblades or butterfly knives.
[Nappen, Evan(2003), "Are Switchblades Sporting Knives", Sporting Knives 2003: 60-65, ] Local jurisdictions including cities and counties may also restrict the ownership or carrying of gravity knives.
In a few jurisdictions, such as
Colorado
Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
and
New York City
New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
,
courts have periodically attempted to classify ordinary
lock-blade folding knives with a blade that may be opened by centrifugal force (normally, using a flicking motion of the wrist) as a gravity knife, thus making the knife's owner subject to the same criminal penalties imposed for illegal possession of a gravity knife.
The New York statute banning gravity knives has been declared "unconstitutionally vague" by a federal District Court in March 2019. New York State legalized the possession of gravity knives on May 30, 2019 but New York City retains its ban on public transport.
See also
*
Butterfly knife
A balisong, also known as a butterfly knife, fan knife or Batangas knife, is a type of folding pocketknife that originated in the Philippines. Its distinct features are two handles counter-rotating around the tang such that, when closed, the b ...
*
Rampuri
*
Pantographic knife, often incorrectly referred to as a "Paratrooper Knife"
References
{{DEFAULTSORT:Gravity Knife
Pocket knives
Edged and bladed weapons