Security Pins

Security Pins: A Beginner’s Guide

To we lock pickers feedback is absolutely everything. It is our sixth sense, our third eye, our perception within the lock that is beyond ordinary sight. The feedback we sense through our tools is what guides us and without it, we are but lonely souls probing the dark depths, looking for any signs of life — but forever finding none.

So what better way to hinder our lock picking efforts than to distort and defile that feedback we so rely on? To make those sensations that we have spent so long learning to identify act against us rather than for us.

This is the purpose of security pins, to take everything we as lock pickers have acquired — our knowledge, our experience, our techniques, and our developed sense of feel — and plot it against us.

So is this the end? Are security pins where lock picking goes to die?

Not even slightly. This is where our lock picking skills will flourish!

While security pins may disrupt the feedback that we have come to know and understand, they also provide us with some additional types of feedback that not only SCREAM to us that they are security pins, but also guide us in easily picking them. Ironically enough, once you understand these crafty little pins, they can actually make a lock very easy to pick.

However, to how to identify and pick a security pin, we first need to understand how they work. So let’s first start there.

NOTE: If you are at all uncomfortable or uncertain of what the shear line is, how a basic pin tumbler lock works, or the process of picking them, I highly recommend reviewing our basic lock picking guide before continuing.

What is a Security Pin?

The most vital component of lock picking is the torque — the rotational tension — that we apply to the lock’s plug. Without this torque, we would not be able to bind the driver pins nor set and hold them at the shear line.

To better understand this, let us briefly review how a pin is set on a simplified lock.

We pick a standard pin by applying tension and pushing it to the shear line. Once at the shear line, the plug will rotate and the pin will set on top of the plug

As we can see, we set the driver pin by first binding it with rotational torque on the plug and then raising it to the shear line. Upon reaching the shear line, the pin breaks the bind and sits on top of the plug — thus “setting” the pin.

So if we think about it, to hinder a lock pickers efforts, there would have to be some method of stopping the driver pin from reaching the shear line if –and only if — the plug is under tension.

So how could this be done?

The First Security Pin

In 1865, Linus Yale Jr. (inventor of the modern pin tumbler lock) took a first step in solving this problem by slicing a notch into the driver pins (Patent US48475). This simple modification would cause the driver pins to “catch” at the shear line if the plug was lifted under tension.

Let’s look at a simple example of this in action.

The first ever security pin developed by Yale

So as we can see, while the driver pin is under tension and lifted, it rubs against the wall of the plug until the notch meets the shear line and snags. However, this snag is not only significant because it stops the pin, but also because it fools the lock picker into believing the pin is set at the shear line when it is in fact under-set.

This state of being snagged and under-set is what we call a “false set” and is the fundamental principle behind the security pin.

The False Set

So besides the driver pin being snagged and under-set at the shear line, there are two additional factors of the false set that add to the trickery of fooling us lock pickers into believing that we have correctly set the pin.

1. The first of these two deceptions is that upon being falsely set, the gap in the security pin will break the bind and allow the plug to rotate until it once again finds the nearest pin to bind on (See Binding Order). This rotation is very similar to what we feel when a pin is correctly set at the shear line.

However, depending on the type of security pin used — as we will soon see — and the depth of the cuts into the pin, this rotation can often be very dramatic. If there is a huge degree of rotation in the plug, as you will come to learn and recognize, it is typically a crystal clear sign that we are dealing with a security pin.

2. The second of these deceptions is that when the driver pin is falsely set, it will no longer be active in the keyway. This not only tricks the picker into believing the pin is correctly set at the shear line, but will also lead them down the frustrating road of finding the next binding pin — which they will never find because it’s jammed at the shear line and not in the keyway.

This will often lead pickers to the conclusion that they over-set a pin, causing them to release tension, drop the pins, and start again. However, like before, they will find themselves in the same aggravating situation as they once again push the security pin to a false set.

This is the power of security pins.

Before we jump into the primary types of security pins and how to pick them, it is absolutely crucial that we understand one last concept — counter rotation.

It’s short I promise!

Counter Rotation

So what would happen if we continued to push at a notched security pin that was in a false set? Let’s take a look.

A security pin straightening out as we place pressure on it to attempt to set it


As we can see, something incredible happens. As we push at the pin, it attempts to straighten itself by pivoting around the area in which it is snagged. This directly causes the opposite side of driver pin to push back against the plug causing it to rotate in the opposite direction that we are applying torque, thus the term counter rotation.

Counter rotation is crucial for two reasons.

1. It is a clear indicator that we are dealing some type of security pin and that the pin is in a false set.

2. It aids us in picking the security pin by counter rotating the plug just enough to push the pin past the jamming point and to the shear line.

Now that we fully understand the fundamental principles behind the security pin, let us finally dive into the most common type of security pin – the spool pin!

Spool Pin

Acquiring its name from its seen resemblance to a spool, the infamous spool pin has the same diameter as a standard pin on both its top and bottom segments, however, has a wide horizontal serration making it narrower along its midsection.

The most common type of security pin used in locks today is the Spool Pin.

First developed in 1865 by Linus Yale Jr. (founder of the Yale Lock Company), the spool pin — due to the simplicity of its design and the ease of manufacturing it — is the most commonly used security pin in locks today.

But with this simplicity comes a cost. As we will soon see, the spool pin is not as sneaky as it tries to be. Due to its design, this pin is insanely easy to detect when in a false set and once detected, just as easy to pick.

Identifying a Spool Pin

So how do we go about identifying a spool pin? Because of their design, once the upper and wider section of the spool pin cross the shear line, the plug will rotate significantly more than a standard pin because it has more distance to travel before it stops on the narrower than usual midsection. It is this significant rotation that warns us of a spool pin and the potential of a false set. Additionally, the bottom ridge of the pin will catch at the ledge of the shear line, causing the pin to stick.

There is an additional step to verifying that you are in fact stuck on a spool pin. While maintaining light tension on the plug, apply a more than usual upward force on the pin. If you are indeed caught on a spool pin, the bottom ridge of the pin will slightly push back against the plug as you place pressure on the pin. You will feel an increase in pressure on your tension wrench as the plug slightly rotates in against it. This backwards pressure on the plug is illustrated below.

Identifying a spool pin by applying pressure to it and feeling counter rotation

Picking a Spool Pin

So now that we have identified our spool pin, the question remaining is how do we go about picking it?

The answer is quite simple. All we have to do is very slightly lighten up on the pressure applied to the tension wrench and begin very gently pushing on the spool pin.

As you push on the spool you will experience counter rotation — this is good and means you are doing it right.

Continue raising the pin until you feel it set — a click or vibration like you would feel by setting any other pin.

That’s all there is too it! Easy right!

There are however two common issues that you may run into while attempting to pick these pins.

The first is that because the spool pin causes the plug to counter rotate, some pins that you had previously set could drop back into the plug. This is normal so don’t fret if you have to re-pick pins you have already set.

The second problem is that of over-setting a pin. This occurs when you apply too much force to where the key pin is pushed past the shear line and sticks.

An overset pin

This problem can sometimes be remedied by release a small amount of tension on the plug and tapping on the pin in hopes of jarring it back into the plug. However sometimes over-setting pins may be grounds for release all tension and beginning again!


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I have worked with many of these drivers. Your animated diagrams are very good at showing the action inside the cylinder. You are using the “pick up” method which can be challenging or near to impossible. I found that raising all the drivers above the shear line then with light controlled raking slowly allow them to come down to the shear line. Neither way is 100% sure but sometimes this way is quicker.


Yes… Exactly! I call it “reverse picking”. I only found security pins in Russwin locks.


Hi. thank you very much for that helpful illustration. My question is. are there any special picking tools for security pins that can make the job easier? if not, what are some good picking tools that can deal with these pins?

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Im a total novice. All there techiques and tips have been a great help !

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What an awesome and very clear explanation of security pins and how to deal with them. Using your information I finally successfully picked a Yale lock which uses spool pins. Such a pity I can’t take it apart non-destructively.

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