What are “Gravity Knives” and “Flick Knives”?
This blog post IS NOT legal advice.
Under UK law, the terms “gravity knife” and “flick knife” (also sometimes known as a switch-blade) refer to specific types of folding knives as defined by how the blade opens/deploys. These definitions come from the Restriction of Offensive Weapons Act 1959 (as amended).
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A flick knife is any knife whose blade “opens automatically from the closed position (or a partially open position) to the fully open position, by manual pressure applied to a button, spring or other device in or attached to the knife.”
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A gravity knife is any knife whose blade is “released from the handle or sheath by the force of gravity or the application of centrifugal force,” and then locks open by means of a button, spring, lever or other device.
In short: flick knives open automatically (button, spring, etc.), and gravity knives open via gravity or ‘centrifugal’ force.
Because of those definitions, both flick and gravity knives have been subject to very strict legal control in the UK for decades. The supply, sale, importation, and possession of such knives is prohibited. However – there is some difficulty in interpreting the specific wording because of poorly worded legal definitions.
Why Ball-Bearing Knives, Flippers or One-Hand Folders ≠ Gravity/Flick Knives (in principle)
It’s common in knife-enthusiast circles to hear concern or confusion about whether modern knives – especially ball-bearing or flipper knives – fall under the banned categories of flick or gravity knives. The short answer (under the law as written) is: no – if they open manually by hand and not by a button/spring or by gravity/centrifugal force, they should not be caught up in the legislation.
To explain:
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“Manually opening” a knife – for example, using a thumb stud on the blade, or pulling it open by hand – does not fall under the legal definition of a flick knife. That’s because a flick knife must open automatically (via button, spring, or similar) to be prohibited.
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Similarly, a flipper or ball-bearing folder that merely uses manual force (your thumb or fingers) to pivot the blade out – even if it’s very smooth or quick – does not rely on gravity or a spring, and so should not meet the definition of a gravity knife.
The updated legal definition of flick knives (post-2019 amendments under Offensive Weapons Act 2019) continues to draw the line at “automatic” opening. This is the ‘intended’ outcome of the legislation. It was targeted to prohibit automatic and more specifically, spring assisted knives.
That means many one-hand folders, “manual flippers,” or ball-bearing knives – common in the knife-enthusiast and outdoor-tool markets – are, at least in principle, outside the scope of what the law bans as flick or gravity knives.
Indeed, when someone interested in knives hears gravity knife they picture a very specific design, or one of a few very specific designs. That is to say – a press button with the blade pointed toward the floor at which point the blade ‘falls’ out and locks into place.
The problem happens when someone tried with all their might to swing a knife as hard as they physically can to cause the blade to open. Sometimes they will claim this is a gravity knife, or a centrifugal knife. This is not the spirit of the law. Which was intended to ban the knives we all immediately recognise as gravity or centrifugal knives.
Ultimately, while it might be possible to open some knives this way, this is not how they were intended to be operated. It’s difficult, unwieldy and inefficient. Not to mention fairly dangerous to yourself. It is our opinion, and that of many other industry leaders in the UK – that this doesn’t cause all folding knives to fall into the gravity knife category. (Obviously) The designers clearly never intended this to be the method of operation.
What’s Banned Under UK Law — And What Might Trigger Misunderstanding
Because flick knives and gravity knives are explicitly outlawed by name, the sale, importation, possession (even in private) is prohibited.
But there are a few reasons why confusion arises (and why someone might get in trouble even with a manual knife):
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The 2019 update to the law broadened the definition of flick knives to capture newer designs that open “automatically … by any manual pressure … applied to a button, spring or other device … contained … in or attached to the knife.”
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Because of that, some retailers and customs officers treat certain folders (especially flipper knives) as if they were banned flick knives. This has led to confusion and inconsistent enforcement. To be clear – flipper knives are not flick knives. Nor are they gravity knives.
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The law gives no real “grey-area” defence: the definitions are mechanical. That means that even if a folder doesn’t look like a classic “switchblade,” it could still be seized if someone (often incorrectly) interprets its opening mechanism as automatic or assisted.
- The best course of action is to calmly explain how the knives are manually operated, contain no springs and in the case of gravity knives are not opened solely by the force of gravity. It’s more confusing if the issue is ‘centrifugal opening’. Any knife that folds and is considered a folding knife could be opened, in theory, by swinging it hard enough. But unless it’s INTENDED operating is centrifugal; i.e a ‘Balisong’ this is not going to reclassify a normal manual folding knife into a gravity opening knife.
Why This Matters — And a Final Word
The legal ban on flick knives and gravity knives reflects concerns about public safety. But for many outdoor, utility or general-use knives (cutting rope, carving wood, campsite use, etc.), there is no inherent reason why a manual folding knife should be problematic – and the law (somewhat) recognises that distinction.
So to this end we consider a gravity knife to be a knife that can be held pointed toward the floor and opened by pressing a button or switch without any other input from the user under the force of gravity. (The same force of course that would cause a ball to hit the floor if you dropped it). We also consider Balisongs to be a kind of gravity knife due to the inclusion of centrifugal force in their legal definition. I.e. That’s a knife that is intended to be opened by ‘swinging’ it arounds it’s handle pivots.
We consider flick knives to be anything that’s automatic. Spring assisted knives are considered automatic and are thus banned. If you can press a button and the knife opens itself. It’s banned. If you have to do the work to open it yourself. It should be considered a manual knife.
Here at Knife Warehouse we have carefully curated our range. We don’t stock any knives that are illegal.
In closing: this is not legal advice. If you want to buy, sell, import or manufacture knives in the UK – or are unsure whether a certain design could be interpreted as illegal – you should consult a qualified legal professional.
Final Note;
We don’t like the term centrifugal force being used in law. It is a ‘fictitious force’ that is the apparent result of an objects inertia. The force doesn’t actually exist per-se – which is quite an interesting read. See: https://en.wikipedia.org/wiki/Centrifugal_force
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