The Most Comprehensive Guide to Lock Security Pins

Key Takeaway

  • Security pins are specially designed pins integrated into pin tumbler locks to enhance their resistance against picking and manipulation, adding an extra layer of complexity to the lock mechanism.
  • There are different types of security pins – spool pin, mushroom pin, serrated pin and hybrid pin.
  • Spool pins are the most common security pins used in locks.

If there is one thing that we, the lockpickers, rely on the most is the feedback. It is our north star that guides us and makes us better in our skills i.e. picking the lock faster. Given this context, naturally the lock manufacturers want to mess with it and make our lives difficult by creating mechanisms that defile this feedback. And that’s how security pins came into this world. 

But having said that, we should not make security pins our enemy. Both of us, security pins and the lockpickers, can cohabit. In-fact, I will go on to say that if we can learn the feedback of security pins, we can actually treat them like a normal pin.

In this (perhaps) the most comprehensive guide about security pins, I will cover every minute detail about them including, what they are, different types, how to identify them and how to pick them. Trust me, it is going to be a fun ride.

What are Security Pins?

What are Security Pins?

Security pins are specially designed driver or key pins that work on the principle of obstructing the sheer line when put under pressure other than a correct key. They bind between the plug and the cylinder thereby restricting the plug rotation. 

They provide effective protection against lock picking, bumping and impressioning. However as we will see later in the article that though these pins do provide some deterrence but with skills (and knowledge), they can be picked like any other normal pin. 

But first, let’s understand how they operate and provide deterrence.

Science Behind Security Pins

Pin tumbler locks work on the principle of aligning pins at the shear line to allow the lock cylinder to rotate and unlock. 

Science Behind Security Pins

As is shown in above animation, the key with the correct cuts lifts up key and driver pins to the right height, aligns them with the sheer line thereby making the core free to rotate; hence opening the lock. 

In lock picking, we try to mimic the same behavior by applying rotational torque (with a tension wrench) and manipulating each key, either one at a time (single pin picking) or multiple pins, known as raking. When a pin is lifted to the correct position (sheer line), we call it a set pin

The biggest tell tale sign of a set pin is increased rotation of the core. Keep this point in mind as this will become the basis of knowing whether you are dealing with a security pin or not when picking a lock.

Now, let’s put ourselves in manufacturers’ shoes and take a moment to think about what can be done to deter lockpicking.

I am sure the answer would have come naturally to you.

You would have to stop the driver pins to reach the sheer line or the driver pins should obstruct the sheer line. Simultaneously, if the mechanism could give a false tell-tale sign of increased rotation, then not only would you have deterred the lockpicker but also made a fool out of him. 

Security pins do exactly that.

How Do Security Pins Work?

So we learnt that the purpose of security pins is to obstruct the sheer line. Let’s see how they actually do it.

How Do Security Pins Work?

Security Pins Obstructing the Rotation of the Plug

As shown in the first image above, when you put tension on the plug and try to set the pin, the security pin (spool pin) notch snags at the sheer line. And this stops the pin from setting. 

Apart from obstructing the sheer line, this spool security pin also does another interesting thing. Since the middle part of the pin is thinner than the edges, it allows the core to rotate a little bit more freely making the lock picker believe that the pin is set. 

In lockpicking parlance, this is known as the false set.

False Set

When a driver pin is under set i.e. below the sheer line and gives a false positive feedback of being set, it is known as a false set. 

Now false set fools any lockpicker by 2 means – 

  • When a pin is falsely set, the gap caused by the security pin will break the bind resulting in the plug rotating. This is the exact feedback that we get when we have set a pin correctly. 

However, depending on the cuts and shape of security pins, this plug rotation could be more than usual. And if this happens, then you know that you are dealing with a security pin. 

  • Another deception that security pins lead us to is moving on to the next pin in the binding order. But since the first pin is falsely set, it will not be active in the keyway therefore we will never be able to find the next pin in the binding order.

Given this situation, we will believe that we would have over-set some pin and hence we would release the tension on the plug. And once that happens, the falsely set pin will come back to its original state leading us into a rabbit hole. 

We have seen the power of security pins, so does that mean that they can’t be picked? Of-course they can!

We lockpickers are a stubborn lot. I will show you just how but let’s first understand another important concept which will come in handy while learning how to pick security pins.

Counter Rotation

Counter rotation is a phenomenon that is exhibited by security pins when they try to straighten out thereby putting counter pressure on the plug. 

Let me explain it with an example – 

Counter Rotation

As shown in the above image, when we try to put more pressure on the pin that is snagged at the sheer line, it tries to straighten itself. This causes the opposite side of the pin to put pressure on the plug. This pressure is in the opposite direction to our torque; hence the name counter rotation. 

Keep this concept in mind as this is a sure shot way of telling that you are dealing with a security pin. It will also come in handy when picking the security pin.

Types of Security Pins

In this section, we will explore each type of security pin in detail, examining their designs, effects on lock picking, and the skills required to successfully navigate their challenges.

Types of Security Pins

Spool Pins

Spool Pins

Spool pins are named after their shape, resembling a spool or barrel, where the middle portion has a thinner inside diameter compared to the outside diameter. They are the most common type of security pins found in locks.

They were invented by Linus Yale Jr. way back in 1865. 

When you try to lift a spool pin to the shear line, the middle of the pin snags at the sheer line. If you lift it further, it results in counter rotation as explained above. 

How to Identify a Spool Pin

There are 2 ways to know that you are dealing with a spool pin.

  • When the pin snags at the sheer line, the plug will rotate more than usual. This happens due to spool pin design. Since the middle of the pin is thinner than the edges, it allows the core to rotate more than when a single normal pin is set.
  • A false set spool pin will result in counter rotation. Therefore if you feel pressure from the plug when applying tension, you know it is a spool pin.

How to Pick a Spool Pin

We’ve learnt everything about a spool pin that was there to be learnt. Now let’s take a look at how to pick them.

Picking a spool pin works on the simple principle of releasing the tension a bit and then lifting the pin slowly till the time the lower edge moves past the sheer line thereby setting the pin.

I know what you are thinking. If it was so simple, then why did I lay down tons of theories? Well because of these reasons – 

  • Understanding counter rotation was important because instead of releasing the tension, you would have continued to put more pressure thereby resulting in counter rotation.
  • Understanding of the false set and plug’s more than usual rotation will help you understand that you are dealing with a spool pin and not a normal pin.

Please note that counter rotation may cause some pins to drop back into the plug that you may have set earlier. Don’t lose heart if this happens. Try again until you succeed.

Mushroom Pins

Mushroom Pins

Mushroom pins have a beveled cut around their circumference, giving them a resemblance to the shape of an inverted mushroom. While mushroom designs are more frequently used for driver pins, certain lock companies like Mul-T-Lock and ABUS also utilize them for key pins.

Beveled cut of Mushroom security pins

Serrated Pins

Serrated Pins

Serrated pins are designed with light serrations or small teeth along the circumference of the pin. These serrations create additional binding points within the lock mechanism, adding complexity and making the lock picking process more challenging.

When attempting to pick a lock with serrated pins, the serrations on these pins introduce a new element of difficulty. As you apply rotational pressure and try to lift a serrated pin to the shear line, one of the serrations can catch or bind at the shear line. This means that instead of smoothly aligning with the shear line, the serrated pin gets snagged by one of its serrations.

Since the binding of serration with the sheer line often comes with a small clicking sound, it fools a lockpicker into believing that the pin is set. 

Frequently Asked Questions

Q1. Are security pins commonly used in all types of locks?

Answer – Security pins are not found in all types of locks but more in commercial and high security residential locks. 

Q2. Can security pins be used in combination with other security measures?

Answer – Yes, security pins can be used in conjunction with other security measures such as master key systems, electronic access control, and physical security devices to provide comprehensive protection.

Q3. Can I install security pins in my existing locks?

Answer – In some cases, it may be possible to upgrade your existing pin tumbler locks with security pins. However, it is recommended to consult a professional locksmith to assess your specific lock and determine the feasibility of installing security pins.


Security pins play a crucial role in bolstering the security of pin-tumbler locks. By introducing spool and serrated pins, lock manufacturers have significantly raised the bar for unauthorized access. While security pins may initially appear intimidating, they can be picked with some knowledge and practice. 

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Hey! I am Mark. Though I am not a locksmith by profession, but locks have always fascinated me since my teens. And it all started when I got locked out of my house and I had to pick the lock. Since then it has become my hobby to learn more about different kinds of locks, understand their working and methods to pick them up. In due course of time, I have also become better aware of how installing the right lock goes a long way in ensuring iron clad security. I aim to share my passion (about locks) through this blog. If you are also passionate about picking locks or are just looking to beef up the security, hop on the ride.