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What is a Gravity Knife?

Like several other inventions such as computer, penicillin, and radar, a gravity knife was produced during World War II. An interesting piece of engineering, this knife uses gravitational force to propel the blade. ThrillSpire helps you know more about this paratroopers' utility knife.
Rucha Phatak
What Led to its Invention?
The gravity knife was mainly produced to help paratroopers to free themselves from the tangled parachutes. Therefore, the gravity knife was designed in such a way that it could be operated with only one hand.

The gravity knife first originated in Germany. These knives were issued to German paratroopers and flight crew members. These easy-to-open knives were brought to the USA and the UK by the soldiers who took them from German soldiers.

So, what is a gravity knife and how does the gravity knife function, you ask?

A gravity knife is one that has its blade folded in its handle, which comes out with a force of gravity and the motion of a hand. The main purpose of the design is to open the blade with only one hand, while the other is busy.


A blunt-spear point blade is folded in a metal frame that is fitted in the wooden handle.

By flipping up the lever that is on one side of the knife, the user releases the blade from the frame. Due to the gravitational force, the blade opens to its full extent. The blade could be drawn with a slight backhand flick. Flipping the lever back locks the blade in its position.

Closing the blade is as easy as opening it. Flipping the switch again loosens the lock of the blade. By flicking the hand in the forward motion, the user can prompt the blade to come out of the wooden handle, and otherwise, release the switch to keep the blade safe in the wooden frame.


The first gravity knife was produced in 1937 at the time of World War II by the German airforce. It was called Luftwaffe Fallschirmjäger-Messer.

The main purpose of the Luftwaffe gravity knife was to help paratroopers as they jump from the airplanes. The knife was used to cut the tangled ropes of parachutes as the paratroopers landed. As the knife could open with only one hand, it was ideal for the parachutists to free themselves from the parachutes if caught in a tricky situation.

Though it wasn't made as a fighting knife, it was sometimes used for close combats.

The attachments like a marlinespike (a tool used in marine ropework) or an awl of the knife would be used as a prying tool or to untangle a knot.


After the German gravity knife became popular, a British version of the gravity knife was produced by George Ibberson & Co. of Sheffield, England. It was produced for Special Operation Executive and used as a secondary combat weapon. These knives were identical with the German knives, with only difference being that of smooth wooden handles or plastic handles.

Switchblades are commonly mistaken as gravity knives. As opposed to the gravity knives, switchblades are automatic. In these types of knives, the blade is contained in the handle, which opens with the help of a spring after a button is pushed.

Though the butterfly knife comes closer to the gravity knife, there is a difference. The butterfly knife relies on hand movements rather than the gravitational force. In this pocket knife, the handle is divided into two parts, which can be flipped open like the butterfly's wings. Opening the handle by moving the two parts away from each other reveals the knife within.

Other knives similar to the gravity knives are OTF knives, penny knives, etc.


Till 1950, carrying of knives was considered legal. However, the popularity of switchblades and pocketknives increased among youth gangs. These sharp tools were more popularized by the movies as well. Finally, lawmakers argued about the danger that these knives posed, and passed the law to make them illegal in 1954 in New York. In 1958, gravity knives were banned as well. Other states followed the example soon and levied a ban on the possession of knives.

As police started arresting the suspects for possessing banned knives, the law was hugely opposed from law-abiding citizens who carried the knives as utility tools and not as criminal weapons. Many went to jail as they didn't know they were carrying knives, which was illegal.

There were many arrests in 2014 for knife possessions based on the lax definition of the gravity knife in the 1950s' law. Now, the law of carrying knives is under constant amendments. The types of banned knives, places where they are banned, slack in the strict law, etc., change from state to state. However, it is better if people refer to their state laws before carrying gravity knives.