There is a natural tendency to try to improve things. To make them more efficient and foolproof towards their tasks and functions. In this endeavor the security pin was born. The purpose of security pins are to prevent individuals from compromising locks by means of techniques such as lock picking and key bumping. These special pins are designed to catch at the shear line and bind the lock when any other tools other than a key are used. They operate under a concept called a “false set.” This false set is when it appears to a picker that a particular pin is set, but it is in fact “under-set,” or that is to say the pin is still between the plug and the cylinder, blocking the full rotation of the lock.
There are three main variations of the security pin used today: the spool pin, the mushroom pin, and the serrated pin. The purpose of this guide is to help you, the lock picker, understand how each type of security pin operates, how to identify each pin in a lock, and of course, how to go about picking them.
A word of caution before we proceed. Tackling security pins requires a level of proficiency in both single pin picking and utilization of the tension wrench. While learning how to pick security pins can significantly increase your fundamental lock picking skills, developing a feel for lifting and setting standard pins is necessary. I recommend finding some level of comfortably with the basics of standard pin and tumbler lock picking before moving on to security pins.
The most common type of security pin utilized in pin tumbler locks today is the spool pin. These pins have the same diameter as any other pin on both their top and bottom but are narrower in the middle section. This depression on the center of the pin creates a ridge that is designed to catch on the shear line if the pin is lifted while the plug is turned, such as while lock picking.
Additionally, the center of the spool pin is narrow enough to allow a picker to rotate the plug enough to set the remaining pins. This means that the a spool pin will only seize the lock once the remaining pins are set. This typically fools any novice picker into believing that they have set a pin when in fact the pin is “under set” and will still ultimately block the plug from fully rotating once the remaining pins are set. This false belief in setting a pin is called a “false set.”
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.
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 lighten up on the pressure applied to the tension wrench and apply extra force to the spool pin. If done correctly, the bottom ridge of the spool pin will have just enough wiggle room to slide past the shear line, thus allowing you to correctly and fully set the pin.
There are however two common issues that you may run into while attempting to pick these pins. The first is that of un-setting and dropping already set pins. This can be the result of either releasing too much pressure from the tension wrench or from applying too much force to the spool pin while pushing it past the shear line, thus causing the plug to back track enough to allow the already set pins to drop.
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. This problem can sometimes be remedied by release enough tension on the plug to allow the key pin to drop back, but more often than not other pins will likely fall and you will have to start again.
Mushroom pins are very similar to spool pins in the way that they behave. These pins get their name because they vaguely resemble a mushroom. They are slightly tapered and it is this that differentiates them from a spool pin. Because of this slope, a mushroom pin will gradually allow the plug to rotate as pressure is placed on the pin until bottom ridge catches at the shear line and falsely sets
The only real difference between a mushroom pin and a spool pin is how they feel while attempting to set them. While a mushroom pin will also allow the plug to significantly rotate under a false set, it will not rotate as abruptly as a spool pin would because of its gradient.
Mushroom pins can be picked just as you would a spool pin. Release a slight amount of tension and apply extra force to the pin until it wiggles past the shear line. Additionally, these pins also fall victim to the same two issues as spool pins.
The serrated pin is very different from that of the spool and mushroom pin. While these other pins use one ridge to catch at the shear line, serrated pins use multiple. They are designed to exploit the fact that torque must be applied to the plug to have any success at lock picking. By using multiple ridges, they prevent the pin from sliding across the shear line while tension is applied on the plug. They come in many variations, with any number of serrations.
A sickly fact about these pins is that if they are in fact under-set into one of their ridges, they can sometimes cause a very frustrating result of transferring the binding effect to another pin. This means that you could spend a very long time attempting to set pins that simply can’t be set. Additionally, when a serrated pin falsely sets, it will feel exactly the same as a successful set. So how is it that we can recognized these pins?
If you suspect a serrated pin, they can be recognized and defeated by easing off the tension and applying additional force on the pin. If you begin to feel the pin grind and bump against the shear line as the pin slowly continues to raise, you can be fairly certain you are dealing with a serrated pin. A sure way to minimize the trouble these little devils can throw your way is to just assume that every pin you pick could be serrated and to test each one as you go.
Practicing With Security Pins
As any seasoned lock picker knows the path to proficiency is practice. You can purchase security pins in bulk at just about any locksmithing website on the web, but if you do not have the resources, time, nor desire to re-key a lock with security pins for the sake of practice, there are many pre-made tools available. One such is SouthOrd’s cutaway spool pin lock for practice with spool pins. Another is GSR Enterprise’s repin cutaway lock in which any novice can repin with any variety of spool, mushroom, and serrated pins. Either is a great investment for furthering your lock picking skills.
Images derived from Deviant Ollam’s Lock Diagrams, available under a Creative Commons Attribution-Noncommercial-Share Alike license.