Yes, you can legally buy and own a lock knife in the UK, as long as you are 18 or over. What you cannot do is carry one in a public place without a good reason. The "under three inches" rule that people half-remember only covers folding knives that do not lock. A lock knife of any length needs a reason to be in your pocket.
That is the whole answer. The rest of this page explains what counts as a lock knife, what counts as a good reason, and how to choose one if you are buying for the garden, the woods or the workshop.
This is a plain-English reading of the law as it stands, not legal advice. The official wording is on GOV.UK, and if you are unsure about your own situation, ask your local police force or a solicitor.
What counts as a lock knife
GOV.UK's definition is short: a lock knife has "a button, spring or catch that you have to use to fold the knife". If the blade stays open until you press, slide or turn something to release it, it is a lock knife.
That catches more knives than people expect:
- Liner locks and frame locks on most modern folding knives, including our Kombat and Ganzo folders.
- Back locks (the lever on the spine of the handle).
- Ring locks, like the Virobloc collar on an Opinel. An Opinel No.6 and up has the twist collar, so it is a lock knife. The smaller Opinel No.05 has no collar, so it is not.
- Slip joints with a very firm spring are not lock knives. If you can close the blade without operating anything, it is a folding pocket knife.
Fixed-blade knives (a Mora Companion, a bushcraft knife, a kitchen knife) are not folding knives at all, so the pocket-knife exemption never applies to them. They sit in the same legal position as a lock knife: fine to own, carried only with a reason.
The three-inch rule, properly
Section 139 of the Criminal Justice Act 1988 makes it an offence to have a bladed or sharply pointed article in a public place without good reason or lawful authority. It then exempts one thing: a folding pocket knife with a cutting edge of three inches or less (7.62cm), provided it does not lock.
Three things people get wrong:
- It is the cutting edge that is measured, not the whole blade or the knife. A knife with a 7cm sharpened edge and a longer unsharpened section at the base is still under three inches of edge.
- Both conditions have to be met. Under three inches and non-locking. A 6cm locking blade is a lock knife and needs a reason. A 7.5cm non-locking blade is over the limit and needs a reason.
- The exemption is about carrying, not owning. You can own a 12cm lock knife at home without any reason at all.
So the one knife you can keep in your pocket day to day without thinking about it is a small, non-locking folder. In our range that is the Opinel No.05, with its 6cm blade and no collar. Everything else we sell is carried for a purpose or kept at home.
What "good reason" means
The law does not list every acceptable reason. GOV.UK gives examples: using the knife for your work, religious reasons (the kirpan carried by some Sikhs), or as part of a national costume. In practice the reasons that come up for the knives we sell are:
- Carrying it to and from the job it is for. A gardener taking a lock knife to a client's hedge. A bushcrafter walking into the woods with a Mora on their belt for the weekend. A camper packing a folding knife for the trip.
- Transporting it after buying it, or to be sharpened.
What is not a good reason, and this is worth being blunt about:
- Self-defence. Carrying any blade for self-defence is not a lawful reason in the UK, full stop.
- "I forgot it was in my pocket." Forgetting is not a reason.
- "It's just a small one." If it locks, the size does not matter.
- "I might need it." A knife carried in case is a knife carried without a reason.
If you are charged, a court decides whether your reason was a good one. The way to make that an easy decision is to keep the knife with the kit for its job (in the rucksack with the tent, in the tool bag with the secateurs), and to leave it at home when you are going to the shops.
The penalty for carrying a knife illegally is up to four years in prison, an unlimited fine, or both, and a second conviction normally means prison. That is why we would rather lose a sale than sell someone a lock knife for the wrong reason.
Knives that are banned outright
Some knives cannot be owned, sold, imported or given away at all, whatever the reason. GOV.UK's list includes flick knives and other automatic knives, gravity knives, butterfly knives, disguised knives, push daggers, belt-buckle knives, zombie knives and zombie-style blades, and, since 2025, ninja swords. We do not stock anything on that list and never have. If a knife opens itself, or is designed to look threatening rather than to cut, it is not a tool and it is not for sale here.
Buying a knife in the UK: age and ID
It is illegal to sell a knife to anyone under 18 in England, Wales and Northern Ireland (in Scotland, 16 and 17 year olds may buy cutlery and kitchen knives, and nothing else). Since 6 April 2022, under the Offensive Weapons Act 2019, bladed items bought online must be handed to an adult, so every knife we send goes out age-restricted and the driver asks for ID at the door. If nobody over 18 is in, it goes back to the depot rather than being left in the porch. Build that into your delivery plans; it is the one thing customers tell us they wish they had known.
Choosing a lock knife (or not)
Start with the honest question: where will this knife live?
In your pocket, every day. Then you want a non-locking folder with a cutting edge under three inches, and you want to accept what that means: a lighter knife for cutting string, opening parcels and sharpening a pencil, not for splitting kindling. The Opinel No.05 is the obvious one, and at 6cm it is well inside the limit.
In the rucksack, the tool bag or the kitchen drawer, used for a job. Then a lock knife is the better tool, because a blade that cannot fold onto your fingers is safer under load. Choose on three things:
- Blade length. 7cm to 9cm does almost everything a folding knife should: food, cord, feather sticks, tent pegs. Longer folding blades add weight without adding much use; if you need a long blade, buy a fixed blade.
- Lock type. A back lock or ring lock is simple and easy to clean. A liner lock is quicker one-handed. None of them is "better"; pick the one your hand finds easiest to release with cold fingers.
- Steel. Carbon steel (the Opinel classics) takes a sharp edge easily and rusts if you put it away wet. Stainless (most Kombat and Ganzo folders, the Mora Companion) forgives neglect and holds an edge a little less keenly. For a knife that lives in a damp rucksack, we would choose stainless.
For bushcraft, camping and any serious wood work. A fixed blade, not a folder. The Mora Companion is the one we sell most of in that category and it costs less than most lock knives.
What our own buyers choose
Looking back over a year of our own orders, most of the folding knives we sell are lock knives, with the Elite / Gator and the TD250 the two that go out most often, and the Mora Companion fixed blade outsells every folder but those two. The non-locking Opinel No.05 is a steady seller but a small one. That pattern tells you what people are actually doing with them: buying a knife for the garden, the allotment or the campsite, where a locking blade or a fixed blade is the sensible tool, and keeping it with that kit. Nobody is buying a 12cm lock knife to walk round town with, and nobody should.
Quick answers
Can I carry a lock knife for work? Yes, if the knife is for the work and you are going to or from it. A gardener's lock knife in the van with the tools is the textbook good reason.
Can I carry a lock knife while camping or hiking? Carrying it for the trip, with the camping kit, is a reason. Carrying it on the train into town the day after is not.
Is an Opinel legal to carry? The No.05 is a non-locking folder under three inches, so yes. The No.6 to No.12 have the locking collar, so they need a reason like any other lock knife.
Is a lock knife under three inches legal to carry? No, not without a reason. The three-inch exemption is only for knives that do not lock.
Can a 16 year old buy a knife? Not from us, or from any UK retailer: the age is 18. In Scotland, 16 and 17 year olds may buy cutlery and kitchen knives.
Do you check ID? Yes. Every blade we send is age-restricted and the courier asks for ID on delivery.
If you are still not sure which knife fits what you want to do with it, email us before you buy and tell us the job. We reply within 24 hours, and we would rather point you at the £7.50 knife that is right than the £30 one that is not.
Related: Machete Buying Guide: Survival, Bushcraft and UK Law covers the zombie-style rules and large blades in detail.
