Folding Knife Lock Types: How Each Lock Works and How to Close It

Short answer: most folding knives you can buy today use one of five locks. A liner lock or a frame lock (a spring leaf you push sideways to close), a back lock (a bar on the spine you press down), a button lock (a plunger you push), or a crossbar lock like Benchmade’s Axis (a bar you pull back). Slip joints and friction folders don’t lock at all. Below is how each one works and how you release it.

A folding pocket knife is exactly what it sounds like: a small foldable knife that you can carry around in your pocket. Even though it is quite handy, not all people carry folding knives but almost everyone is familiar with these tools. Pocket knives have a rich history and come in hundreds of styles. You can choose from a whole array of features for what suits your needs and preferences.

If you are a pocket knife enthusiast, then you would already know that there’s more to this item than just the blade’s material or the handle’s functionality. But if you aren’t, and are looking for some useful tips to help you choose lock knives that fit your personality, you should know that the knife lock system is among the most essential criteria when choosing folding pocket knives.

Locking systems are mechanisms that stop the knife from folding onto your hand during use. We have compiled below a comprehensive lock guide to help you decide what kind of knife lock is most suited to your needs and that you would find easiest to handle.

Generic Lock Systems

Most folding knife lock types available in the market are generic, meaning that the lock design makes its use easy for everyone. Because of that, these lock designs are popular amongst folding knife manufacturers and are widely used.

Below are some generic locking mechanisms that you will find in most of the folding knives you see during your search.

Friction Folder

This type of knife lock is not really a lock. There are no locking mechanisms in the knives that you can call a lock. These knives simply consist of blades, fulcrums, and simple handles. The only thing remotely close to a locking mechanism is an extension of the blade’s tang (often called the kick or lever) that sticks out of the handle when the knife is open. It stops the blade from swinging past open, and you keep it closed against the handle with your fingers while you cut. Let go of it under pressure and the blade can fold.

Although this knife can be unsafe when used by an amateur, it is the oldest knife we have listed. Proof of its usage goes as far as the time of the post-Republican ancient Rome. To close it, hold the handle firmly in one hand and fold the blade with the other, pushing on the spine, never on the edge side.

Slip Joint

This type of knife, also, does not technically have any locking mechanisms in place but it does have another mechanism that makes it safer than friction folding knives: a backspring in the handle presses on the flat end of the tang. That spring holds the blade closed until you pull it open, often clicks it into a half-stop at about 90 degrees, and holds it fully open. It resists closing, but firm pressure on the spine will still fold it, so cut with the edge away from your fingers. This slip joint system is found commonly in Swiss military knives and Boy Scout knives.

Liner Lock

A liner lock is very common in folding pocket knives for everyday use. The liner lock system comprises a stainless steel spring along the handle cavity (where the knife rests when turned) that springs in behind the tang when the blade opens and prevents the knife from folding back down. To shut the blade, you push the liner sideways with your thumb until it clears the tang, then fold the blade with your other fingers out of its path. Liner locks are very common and rarely need repair, but they wear: over the years the liner travels further across the tang. If it slides all the way over to the far side of the handle, or the blade wiggles when you press on the spine, the lock needs attention from the maker.

Frame Lock

The frame lock (also known as the Reeve Integral Lock) is very similar to the liner lock; however, it is more sturdy and simple. A section of the handle frame is cut and bent so it springs in behind the tang once the blade opens, and you push it aside with your thumb to close. What’s the difference, then, between frame locks and liner locks? The frame lock is a part of the handle itself instead of being added inside the handle scale in the form of a liner. As a consequence, the lockbar is thicker, so the frame lock is usually stronger than a liner lock and needs less maintenance.

What steel is the lockbar of a folding knife made of? On frame locks it is usually titanium, because the whole handle side is titanium, and on cheaper knives stainless steel. Titanium can stick or wear against a steel tang, so many titanium frame locks have a small hardened steel insert where the lockbar touches the blade. Liner locks use a stainless steel or titanium liner.

Back Lock

When it comes to Back locks, these are slightly less used compared to their liner and frame counterparts. These are found in many classic American knives. It works differently from liner and frame locks: a rocker bar runs along the spine of the handle, and a spring pushes its front end down into a notch on the tang when the blade opens.

To close it, press the exposed end of the bar near the back of the handle (as the name suggests). That lifts the hook out of the notch and the blade can fold. On stiff traditional back locks this sometimes takes two hands. Back locks are strong, work the same for either hand, and suit people who don’t like pushing a liner across with their thumb.

Button Lock

Button locks are much less common than all the knife locks we’ve listed so far. They are mostly used in automatic knives and require no significant labor on the user’s part in deploying the knife.

The button in these knives serves two purposes: it prevents the knife from opening when it is shut by being held in an aperture at the base of the handle; and second, it prevents the knife from closing when the knife is triggered open by notching into another slot in the handle.

This lock type has been modified slightly and used in manual knives also such that it holds the knife ajar with only slight resistance when trying to close, and also makes it easier to open.

Lever Lock

The lever lock works on a similar principle as the button lock, but you press a pivoting lever set into the handle (often in the bolster) instead of a button. On an automatic knife, pressing the lever releases the blade, and the same lever holds it open. To shut the blade, you press the lever again and fold the knife. This lever lock mechanism is mostly found on automatic knives, such as classic Italian stilettos.

Clasp Lock (Navaja Ring Lock)

“Clasp knife” is an old name for any folding knife, but the clasp lock people usually mean is the one on traditional Spanish navajas. A long spring on the back of the handle catches the blade when it opens, often with a ratcheting click on the way. To close the knife, you lift the ring or tab at the back of the spring, which pulls it out of the blade’s notch.

Mid Lock

The mid lock is basically a variation of the back lock, but the release sits in the middle of the spine instead of at the back. It works and closes the same way: press the exposed part of the bar and fold. Makers use it when they want a differently shaped rear of the handle, as on many traditional patterns. Because the release sits under your hand, hold the knife so your palm doesn’t press it during hard cuts.

Proprietary Lock Systems

Also known as brand-specific lock systems, proprietary lock systems are knife locks that have been developed by a particular knife manufacturing brand exclusively for their own products. This means that unless a licensing agreement is involved, you won’t find them on any other knives. Of course, simply because a company has proprietary locks doesn’t mean all their knives incorporate it. But as a user, you should know your way around some of the most common ones.

Arc Lock (SOG)

On the face of it, SOG’s Arc lock seems to work similarly to a button lock. But there are some big differences between the two. A spring-loaded stud runs in a curved slot in the handle, which is how it got its name, and the spring keeps pushing it toward the blade.

When the blade opens, the stud snaps into a notch at the back of the tang and keeps the blade from closing. To shut the blade, you pull the stud back along its arc, which frees the tang so the blade can swing back inside the handle. It works the same for either hand.

Axis Lock (Benchmade)

Axis lock functions in much a similar way as the Arc lock above although they are different enough to have had separate patents filed for each design. A spring-loaded steel bar runs across both sides of the handle above the tang. When the blade opens, the springs push the bar into a notch at the back of the tang, and the bar wedges against it so the blade can’t swing back.

To release the Axis lock, you pull the bar back toward the butt with your thumb on either side, and the blade swings closed. It is fully ambidextrous and very secure. The small omega springs can break after years of flicking, but they are cheap to replace. Benchmade’s patent has expired, so many brands now sell similar crossbar locks under their own names.

Compression Lock (Spyderco)

The compression lock is one of the most inventive lock designs out there. It is built on the liner lock: a leaf of the liner springs into place when the blade opens. The difference is where it sits.

The leaf is reached through a cutout in the spine of the handle, and it wedges sideways between the tang and the stop pin. Pressure on the back of the blade squeezes the lock tighter instead of pushing it loose, which avoids the liner lock’s main weakness. To close it, press the leaf sideways through the spine cutout and fold the blade, keeping your fingers clear of the edge.

Tri-Ad Lock (Cold Steel)

Cold Steel’s Tri Ad lock was developed by Andrew Demko and is a kind of back lock but slightly different. It operates the same way as a regular back lock: press the exposed bar on the spine to close the blade. The difference is a second stop pin set behind the lock bar. When you put force on the spine, the bar is pushed against that pin, so the pin takes the load instead of the small hook. That makes it one of the strongest locks you can carry, though closing a stiff Tri-Ad often takes two hands.

Virobloc Safety Ring (Opinel)

The Virobloc Safety Ring (also known as the Collar lock) is, without any exaggeration, a sheer stroke of brilliance. It is not only simple to operate and hence convenient to use, but also much more secure and reliable than you would expect from something so simple, a heaven-sent combination. The ring sits around the metal bolster at the top of the handle and has a gap cut into it.

The bolster also has a slot through which the blade can swing. Turn the ring so the gap lines up with the slot and the blade moves freely. Open the knife, twist the ring, and its solid part blocks the tang so the blade can’t close. Twist it the other way with the knife closed and the blade can’t open in your pocket. It holds well for everyday cuts, but it only works if you remember to turn it, and the smallest Opinels (No. 2 to 5) have no ring at all.

Ball-Bearing Lock (Spyderco)

This locking system was first designed and developed by Sal Glesser and improved by Eric Glesser for Spyderco. It works much like the Axis and Arc locks: a spring pushes a ball bearing against a ramp on the blade’s tang, wedging the blade open. To close it, pull the ball’s release back with your thumb and fold the blade. It is actually an interesting lock to use once you get some experience with it!

Final Thoughts

Despite knowing all the lock types, there is no one correct answer to the question of which knife lock is the best. Different lock types suit different knife styles, different purposes, and unique user requirements. For example, left-handed users should be careful with liner and frame locks: most are built for the right hand and are awkward to release with the left. Back locks, button locks and crossbar locks like the Axis work the same for either hand. Some users want a lock that is extremely secure, such as the Tri-Ad lock.

Whichever lock knives you choose to use, make sure that they align with your requirements as a user. You’ll find those lock knives that suit your purposes will go a long way with you.

If a lock already gives you trouble, my guide on how to fix a pocket knife that won’t close walks through releasing each type. And if you’re shopping, my picks for the best EDC knife under $100 and the best flipper knife under $50 cover the locks on the knives I recommend.