Let’s dive right in: A gravity knife is any knife with a blade inside its handle, and that opens its blade through gravity alone. That’s it. Pretty simple, right?
Gravity knives are not switchblades or automatic knives — those knives propel their blades open with spring force — even though some state laws lump all these knives into the same “prohibited weapons” category.
Q: How Does a Gravity Knife Work?
A: Gravity knives have blades that open by gravity after the user disengages a lock of some kind. There are two ways gravity knives provide this free-falling functionality.
OTF Gravity Knives
The most common gravity knives open “OTF” or “out the front.” OTF gravity knives have blades that are recessed within the handle. Their blades are held in place by a mechanical stop — usually a pin attached to the blade’s tang. When the pin is moved, the blade is unlocked and falls out of the end of the handle, into the open position. Usually, the pin that holds the blade closed also keeps the blade locked open.
In the case of the Reate EXO Gravity Knife (pictured above), the blade and its stop pin are locked and unlocked by opening the handle scales: The scales act as a lever that, when pulled away from the knife’s frame, disengages the blade’s stop pin, which is fitted to the tang. After the blade falls out, the scales can be closed to reengage the stop pin. This locks the blade in the open position.
Flipper Gravity Knives
Like an OTF gravity knife, the flipper gravity knife (like the Paragon Warlock) stores its blade inside its handle. Except instead of falling out of the handle in a linear motion, flipper gravity knife blades pivot and swing outward, before locking open.
The Warlock’s flipper action demonstrates this in a unique way: Two spring-loaded buttons must be depressed on either side of the handle. This forces the handle to split open. The blade then swings outward from the handle. Releasing the buttons allows the handle to close, locking the blade in the open position.
This quick video, courtesy of Blade HQ, illustrates the Warlock gravity knife’s unique action. Many other flipper gravity knives have simpler actions: One side of the knife’s frame is open, and a pin holds the blade inside. Depressing a single button allows the blade to fall out of the frame, not unlike a typical folding pocketknife.
Technically, any button-locking, folding pocketknife with smooth bearings that allow the blade to fall open by gravity alone (or even a flick of the wrist) could be considered a gravity knife.
Q: Are Butterfly Knives Considered Gravity Knives?
A: No, butterfly knives are not gravity knives. The user must manipulate the rotating handles of this knife to fully open, lock, and close the blade. Although enthusiasts love to flip these knives by performing inertia-assisted tricks, butterfly knives cannot open nor close with gravity alone.
Importantly, some states have banned butterfly knives and gravity knives alike.
Q: In What States Are Gravity Knives Illegal?
A: Delaware and New Jersey are the only states to ban the possession of gravity knives. Delaware Statute 1446 says, “A person is guilty of unlawfully dealing with a switchblade knife when the person sells, offers for sale or has in possession a knife, the blade of which is released by a spring mechanism or by gravity.”
Interestingly, the Delaware law implies that switchblades and gravity knives are the same. They are not; more on that below.
Section 2C:39-3 of the New Jersey Revised Statutes says, “Any person who knowingly has in his possession any gravity knife, switchblade knife, dagger, dirk, stiletto, billy, blackjack, metal knuckle, sandclub, slingshot, cestus or similar leather band studded with metal filings or razor blades embedded in wood, ballistic knife, without any explainable lawful purpose, is guilty of a crime of the fourth degree.”
Q: Are Switchblades The Same as Gravity Knives?
A: No, switchblades are considered automatic knives and deploy their blades using spring force. Gravity knives deploy their blades using gravity alone.
Our Guide to Automatic Knives dives into the various types of auto knives and switchblades, and how they work.