Why Do Most OTF Knives Have Glass Breakers

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Mankind’s earliest tool — the knife — has evolved continuously since its inception. Initially made of wood, bone, and stone, the blades have shifted to metals and ceramics, and the sheer variety of their shapes developed with their purposes. Nowadays, the selection of knives is plentiful and their usefulness doesn’t end at cutting. You might, for example, see a knife with a tiny bevel at the end of its handle. That would be a glass breaker — the main subject of this article. 

Why Do Most OTF Knives Have Glass Breakers

An OTF knife is already great for emergencies due to its efficient blade mechanism. It is a quick and effective tool that can be used in a short amount of time. It also benefits from a long, slim handle that can offer a proper grip when breaking glass. For this reason, an OTF knife is an excellent choice for combining with a glass breaker.

What is a Knife?

A knife is a tool used for cutting, piercing, or slicing. Consisting of a blade and a handle, knives come in a variety of different types — with the most common ones being folding, automatic, butterfly, and, of course, fixed blade. With just how much use one can get from a tool as versatile as a knife, it is no surprise that it is a frequent sight in outdoor or military surplus stores, as part of hunting or camping gear, or simply as an everyday carry (EDC) item. 

What is an OTF knife?

OTF stands for “out the front.” It is a type of automatic knife in which the blade retracts when you press or engage a button or slide. Instead of unfolding from the side, the blade springs out of the front of the handle — hence the name.

OTF knives are fast, snappy, and, thanks to their design, usually pretty slim. Both of these factors combined mean that they are not only easy to conceal but also fast to have ready in case of an emergency. They can either be single or dual action — meaning the blade has to be folded back manually (single) or is done with another engagement of the mechanism (dual). 

What is a Glass Breaker?

A glass breaker, as you can imagine, is a tool whose sole purpose is to break windows. Despite its grand intention, the tool itself is rather small — it is a metal tip. To give you an idea of scale, you can buy a glass breaker attached to a pen, a keychain, or as a handheld plastic hammer. They often come accompanied by a seatbelt cutter as a vehicle emergency set and their effectiveness is dependent on the material they are made from — with the best ones crafted from tungsten carbide

It is important to note, however, that glass breakers do not work on any type of glass. They can only destroy tempered glass, such as that installed as found in the side windows of cars and buses, skylights, mobile phone protectors, some windows in buildings and elevators, and telephone booths. 

What Makes Tempered Glass Special? 

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Tempered glass is heat-treated at a temperature of about 1,150 degrees Fahrenheit (or 620 degrees Celsius), after which it is rapidly cooled using high-pressure air. This process — called “quenching” — makes the outside layer decrease in temperature much faster, leaving the internal layer in tension. The stress created between the layers is what gives tempered glass its unique properties and appearance — the minuscule glass pieces arranged in an almost spider-web-like pattern when the window is struck. 

Why Would You Need a Glass Breaker?

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As we already pointed out, glass breakers are commonly paired with seatbelt cutters. In this combination, they are a powerful tool in any vehicular emergency

They can be the difference between life and death if you ever find yourself in a situation where you cannot access door controls in your car, for example: if your car is submerged in water or toppled over. This also accounts for situations where the vehicle you’re driving has auto-locking doors — potentially trapping you in a dangerous scenario. 

It is always best to be able to create an escape route if you cannot immediately see one. 

What if I Don’t Own a Car?

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You don’t need to be a driver to own a glass breaker — crashes don’t only happen in personal vehicles. Bus and train windows are often also made from tempered glass and are, thus, vulnerable to a glass breaker’s impact. 

But its uses aren’t limited to your own emergency escape. You may be a witness to situations where someone else is trapped in a locked vehicle. This could be a child or animal left inside a car on a hot summer day or even an adult who has just been in a car crash and is awaiting paramedic assistance. Of course, you should always be aware of the laws in your state regarding the legality of breaking a window to rescue a child or pet. 

Why Should I Have a Glass Breaker on My Knife?

If you already carry a knife as part of your everyday carry, it is only logical for it to also have a glass breaker. In fact, a lot of them already come with one and are often called rescue knives — they will also probably have a seat belt cutter.

As the tool itself is rather tiny, having it attached to a larger item with a comfortable handle can make it easier for you to access or achieve a proper strike. Breaking a window can be quite tricky, and you don’t want to hurt yourself doing it, either. The best technique for forced entry is to hit the window at its corners. That way, you can shield yourself from the shattered pieces. Remember: they are still sharp even if they are small and can do a lot of damage, especially to uncovered parts of your body, such as your eyes. 

With OTF knives being generally slimmer and their handles longer to accommodate the length of the blade when retracted, you may benefit from a better grip and thus a better strike. This is much different from other types of knives you might see on the market where the handle is too small or too big and bulky, making it difficult to acquire a firm grasp.  

A glass breaker is also an additional striking point for self-defense. Now, if you’re not able or willing to use the edged part of the knife to stab or slash, the glass breaker can serve as an effective impact weapon. This can also be useful if the blade is broken off or becomes damaged.

In Conclusion

If you’re already carrying a knife to use in emergencies or during outdoor activities, selecting one with a glass breaker is a sensible choice. An OTF knife in particular offers a quick way of retracting its blade and a slim handle to achieve a firm grip. This combination makes them the perfect emergency rescue tool you can confidently reach for if you ever need it.   


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