Using a folding knife is quite simple with a good understanding of the operating mechanism. Indeed, when it is open, it is imperative that it be locked for optimal handling. This is why folding knives are equipped with a locking/blocking system. Given the array of locking systems that exist, it is important to create a guide for those who are not familiar with them.
Liner knives
Liner knives are those whose locking system is based on metal plates made of steel or titanium. These are real locking systems, the safest ones. They include the Liner lock, the Frame lock, and the Axis lock.
Liner Lock
The liner-lock locking system is one of the most popular. It consists of two main metal liners that are either steel or titanium. The handle pillars are fixed on these two liners. One of the liners is shaped to form a spring. In the open position, this spring butts against the blade tang to prevent the knife from closing. It's a very simple system both in locking and unlocking. You'll need to actuate the spring plate by moving it laterally with your thumb while taking care to close the blade with your index finger. On some models, a button allows you to release the locking plate. The liner-lock is often confused with the Frame Lock, which is thicker.
Frame Lock
The similarity between the Frame Lock and the Liner Lock explains the confusion. Indeed, the locking mechanism is the same with the only difference here being that the entire handle locks against the blade tang. This is why this locking system is also called Integral-Lock. Unlocking is done by pressing on the spring with the thumb, which releases the blade. Several Frame Lock models exist. On the complete model, the liner is covered with a scale which is absent in the incomplete model. It's almost impossible to distinguish the liner lock from the complete frame lock. It can be concluded that the Frame Lock is a better version, especially since its liners are most often made of titanium.
Axis Lock
Introduced in 1998 on the Benchmade 710, the Axis lock made its appearance in locking systems. It is supposed to be proprietary to Benchmade knives. However, other brands use it under different names. The Axis lock is an ambidextrous system allowing optimal one-handed use with just a wrist movement. Automatic locking when opening the knife makes it easier to use. To unlock the knife, simply pull the Axis button backwards. Although the liner-lock is the most common locking system, the safest and most secure system remains the Axis Lock.
Pump knives
Encompassing both back-lock and front-lock, the locking and unlocking of these knives rely on the actuation of a spring.
Back lock
The back-lock or lock-back is part of the pump locking systems, just like the front-lock with which it is often confused. It's important to know that the two systems are identical with the only difference being that the lock is at the back for one (Back) and at the front for the other (Front). Only unlocking requires user participation. As soon as the knife is opened, the blade is automatically locked. Pressing on the pump releases the locking rod and closes the knife. It's the French brand Florinox that uses this locking mechanism, notably for its famous Kiana model.
The ferrule
The ferrule locking system is specific to traditional French folding knives. It is found on Nontron knives and particularly on Opinel knives. It's not surprising to hear people talk about the Opinel ferrule to designate the locking system. The ferrule is a steel ring located between the blade and the handle. It consists of a fixed part and a sliding part. To lock the blade, simply manually turn the ferrule and turn it back to unlock.
The two-pin locking system
Friction is the main mechanism of this locking system. It is most often found on older knives because it is quite simple. Thanks to the friction of the blade against the handle scales, the knife is held in the open position. There is a pin in the blade axis and another that serves as a support point for the tang. In this class, there are the Piemontese and the Capucin.
The Piemontese system
The Piemontese is one of the oldest folding knife locking systems. Although knives with this system are still called Vernantins, they are not necessarily of Italian origin. In fact, Higonokamis, which are small folding knives of Japanese origin, also have this locking system. Piemontese-style knives are easy to recognize. The tang of their blade has a protrusion called a lens or magnifying glass. This allows the blade to appear by pressing with the thumb. It also allows the blade to be locked by pressing against the back of the handle.
The Capucin
The Capucin is recognizable by its handle shape resembling a monk's hood. This is where the name Capucin or 'hooded knife' comes from. It is one of the oldest knives used by shepherds. It is simple and lightweight.
The slip-joint closure system
The slip joint closure system includes slip joints, flat joints, Slipits, and Notch joints. These are systems that lack real locking mechanisms.
Slip joint
This closure system is certainly very familiar to you. The slip joint is the locking system for most French regional folding knives such as the Laguiole or Sauveterre. It's also found on Swiss knives like Victorinox. The functioning of this system relies on a spring located at the upper part of the handle. It presses on the blade tang to prevent accidental closing. However, a slight pressure on the back of the blade will allow the knife to close very easily. Therefore, the slip joint is not actually locked. It retains the potential to fold at any time.
Flat joint
The difference between a slip joint and a flat joint is the presence of a notch on the end of the spring in contact with the blade tang. This notch allows for a better grip on the blade.
Spyderco systems
Grouped here are the different locking systems implemented by the American brand Spyderco. There are two and they are essentially based on compression: The Ball bearing lock and the compression lock
Ball Bearing lock
As its name suggests, the Ball bearing lock is a locking system based on ball bearings. It was created by a famous American brand with a spider logo, Spyderco. The Ball bearing works thanks to a ball pushed by a piston. The ball is visible from both sides, making the system ambidextrous.
Compression lock
This is another folding knife locking system developed and patented by Spyderco. A leader in innovation, the American brand created this compression lock system which is super effective and easy to use. A liner located at the top of the handle allows the blade to be locked. Using the thumb, unlocking is very simple.
Other folding knife locking systems
Systems that come from other manufacturers are developed in this section. It is therefore a mix without prejudice of a common mechanism.
Descy lock
This system seems to be a variant of the Ball bearing lock but it does not have balls. Its operation is inspired by a piston system that allows the blade to be locked. The Descy lock, named after its manufacturer, is the result of work by knifemaker Alain Descy.
Arc lock
Developed by the SOG company, this is an ambidextrous system usable with one hand. It is resistant and provides protection for fingers which are not exposed during locking.
Action 2
Action 2 is a locking system found on automatic knives. They have a switch on the handle allowing to switch from automatic to manual use and vice versa. This is a locking system specific to the Boker brand.
If you've reached this point in reading this text, you already know the main locking and blocking systems for folding knives. We wanted to list the most frequently encountered systems. It's important to note that the list described above is not exhaustive. Folding knife locking systems are legion. However, our list is comprehensive in terms of mechanisms; other models on the market are variants.