Locks are actually very simple devices, their security being derived from the unit's ability to hide its combination and be difficult to open without that combination. Improving this security comes from one of two vectors. First, the combination can be made increasingly difficult. For example, a simple lock consists of guessing the "on" or "off" combination of two buttons - four combinations. A more complicated lock would feature 5 buttons for which 5 levels of depression are possible for each - 3125 combinations. The second vector comes from the difficulty the lock presents. A piece of 1/8" metal will quickly fall to bolt cutters, while a piece of 1/2" steel would deter them (if they could even get past the shackle shroud). Security is simply a matter of determining the appropriate level of difficulty for the object to be secured.
Figure A: This simple lock uses only two levers that can be “up” or “down.” It takes at ''most'' four guesses to figure out the combination.
Figure B: This more complicated lock uses five levers that can be put into five positions. It takes at ''most'' 3125 guesses to figure out the combination.
How a Key Works
A traditional lock opened by a key is known as a cylinder lock. These are found everywhere from automobiles and gym lockers to a home deadbolt. They are called cylinder locks because when a key is inserted and turned, a plug within a cylinder spins, driving a cam that pulls back a dead bolt or latch. Such a lock utilizes tiny pins within the cylinder to prevent the central plug from rotating. When there is no key inserted, tiny springs push these pins such that they "straddle" what is called the shear line. The shear line represents the slim boundary between the inner plug and the outer cylinder, like a sleeve. When the pins cross the shear line, it is impossible for the plug to rotate because they are in the way. Each pin is actually two separate pins (an upper and lower) of varying size. When the key is pushed into the lock, the ridges push these pins upwards such that the split between the upper and lower pins align with the shear line. That gap allows the plug to rotate freely within the cylinder, effectively unlocking the lock. Picking a lock is simply the art of setting these pins along the shear line without using a key.
Figure C: In this example, the lock’s pins straddle the shear line which prevents the inner plug from rotating.
Figure D: The ridges on the key push the pins into the appropriate position. The upper pins lie above the shear line and the lower pins lie below the shear line. Because the pins do not straddle the shear line, the plug can now rotate freely when the key is turned.
How to Build a Lock Picking Trainer
Knowing how to pick a lock is more than just reading an article. The technique is very simple, but doing it with any sort of speed and repeatability, as with all things, requires practice. There is no need to sit in front of your house attempting to pick your way in (and making neighbors stare uncomfortably). Simply construct a simple lock picking trainer so you can practice while watching TV or during a boring lecture.1 All the materials necessary for building a lock picking trainer can be found at a local hardware store. After all, the hardware store sells the tools and often the locks that are installed in your home. In addition to typical household tools, the materials required include:
generic dead bolt
hole saw bit
scrap wood
Figure E: For the deadbolt purchased, the trainer required a 2" hole for the locking mechanism and 1" hole for the bolt.
Figure F: The deadbolt consists of three components – the bolt mechanism, the tumbler (for the key and its pins) and the manual lock.
The meat of the construction surrounds preparation of the scrap wood. The example wood measures 6" long by 4" tall by 13/4" deep. Once properly sized, drill the necessary holes into the scrap wood to insert the lock cylinder and the bolt. For this example, the lock unit required a 2" hole to house the mechanism and the bolt required a 1" hole. It helps to use a T-Square to align the holes with one another. With the holes drilled, it is a simple exercise to insert the deadbolt components as depicted in the video below. Any number of on-line tutorials exist for installing deadbolts in an actual door.2 The same method applies for installing one into a piece of scrap wood. With the deadbolt installed, the lock pick trainer is complete.
How to Pick a Lock
At its simplest, lock picking requires two tools: a pick and a torsion wrench. These tools can either be made or purchased.3 The pick is meant to go into the lock just like a key and is used to push pins into the unlocked position. There are a variety of techniques for successfully achieving this. The torsion wrench serves both to rotate the plug (opening the lock) and to apply tension to the pins while picking. While these tools are commercially available via the Internet, it is necessary to check local laws to determine if owning lock picks is permissible. Many state laws indicate ownership is not a crime unless purchased for criminal intent. The word "intent" creates the fuzzy barrier whereupon the policeman's mood determines whether or not you are charged.
Figure G: Traditional lock picking tools are very simple. There is a torsion wrench for applying tension to the pins and turning the plug. Picks come with a variety of head designs to facilitate setting the pins into their unlocked positions.
Figure H: This diagram represents a cross section of the locking cylinder. The cylinder on the left shows how the upper pin prevents the plug from rotating because the shear line is blocked. The cylinder on the right shows how the pins are placed into the proper position by a key for the plug to rotate freely.
Figure H depicts another point of view for Figure D, where a proper key sets the pins appropriately in the shear line for the lock to open. This is the same result that will be obtained by carefully picking the lock. To begin, insert the torsion wrench into the bottom of the keyhole. It should rest as far from the center of rotation as possible to maximize the applied torque and leave plenty of room for the pick to operate. Apply a slight amount of pressure to the torsion bar so that the plug binds the upper pins in the shear line as depicted in Figure I.
Figure I: With torque applied on the plug, the upper pin is squeezed in the shear line between the plug and the cylinder.
The pick can be used in many ways but two are relatively common. Raking is a simple, fast and brute force technique that simply requires "raking" the pick back and forth across the pins. Although imprecise, the action forces all of the pins to move with the hopes that when the spring pushes them back down, the upper pin will be caught on the upper lip of the plug. The second technique involves carefully using the pick to push each pin upwards one at a time to settle the upper pin on the plug’s lip. Both techniques work as depicted in Figures J and K to push the pins between the plug and cylinder until they’ve been separated on the shear line. Once each pin is set, a little extra pressure on the torsion bar will turn the plug and open the lock. Fundamentally, that is all there is to picking a lock.
Figure J: While the friction between the plug and cylinder keeps the pin from falling, the pick is able to push the pins upward towards the shear line.
Figure K: When the upper pin clears the shear line, it will rest on the plug’s lip. Care must be taken not to push the lower pin past the shear line as it will bind and prevent the lock from opening.
Given such simple steps, what keeps everyone from simply opening locks with paperclips and hair berets like the movies and television? As mentioned earlier, lock picking is just like any other activity where the actual practice of picking a lock differs from simply reading the fundamentals. When picking a lock, the first fundamental skills include learning the right amount of pressure to apply, learning to feel the subtle "clicks" through the tools, and learning to visualize the mechanism's state in your mind. Common beginner mistakes include:
Too much pressure on the torsion wrench - If you apply too much pressure here, the plug and the cylinder will bind the upper pin so tightly that it will not move when you're trying to rake or set the pins. When the pins do not move, the lock does not open.
Too little pressure on the torsion wrench - If the torsion wrench is not pushing enough, the intentional misalignment of the plug and cylinder along the shear line may not be great enough. This could result in the upper pin not catching on the plug's lip or the upper pin may keep falling off the lip which keeps the lock locked.
Raking too hard knocks out upper pins - If the raking action is too forceful, even pins that have been correctly set may be knocked back out of place by the impact from the lower pin.
Raking too hard binds lower pins - Another problem with hard raking is that with enough force, the lower pins will be pushed upward into the shear line. When the lower pins are bound between the plug and cylinder, the lock remains locked. This condition is often difficult for beginners to detect.
Trying to set pins sequentially - One way lock manufacturers attempt to deter the basic rake technique is to offset the pins from the plane as shown in Figure L. This means the pins must be set in sequence based on their distance from the plug's lip. Sometimes when a pins refuses to set, it is necessary to attempt setting a different pin first.
Figure L: Picking locks is trivial when all of the pins line up in a perfect plane. Most lock manufacturers will offset the pins slightly which will make the order in which they settle atop the plug’s lip matter.
Summary
A basic lock is very simple mechanism to defeat, especially for someone with appropriate tools who has practiced the technique. Constructing a lock picking trainer enables one to practice discreetly whenever and wherever is most conducive to learning. Practice is the "key" to succeeding in the art of lock picking - in learning the proper amount of pressure to apply on the torsion wrench and how to feel through the pick which pins are properly set. In the video below, note the very light pressure applied to the torsion wrench. The raking technique is demonstrated in the beginning followed by individual pin picking towards the end. Although the video is a composite of two clips, the actual picking of this lock took less than three minutes.4
Closing and Further Considerations
Despite the ease with which a lock can be opened, there is usually always a faster or simpler way. For example, a door may be secured by a top brand lock but a thief can simply break the decorative glass beside the door, reach through the hole and unlock the bolt from the inside. Perhaps an excellent lock secures a chain holding a fence closed - but it does nothing to prevent an intruder from climbing the fence. Security is therefore derived from the complete picture and an abundance of locks alone cannot be relied upon as the sole method of protection. Even after all vectors of ingress are adequately mitigated, lock quality is an often overlooked element leading to a false sense of security. Invest in the appropriate degree of lock quality to secure yourself and your valuables.
Footnotes
I taught myself to pick locks using this trainer during Signal Officer Basic Course at Ft. Gordon. The instructors were droning on about something I already knew so I focused on learning the feel of the picks and was able to open a deadbolt for the first time forty-five minutes later. This skill was the most useful thing I learned in OBC. For what it's worth, I was never able to open a 2600 series lock, but opening the keybox with the keys for all the 2600 series locks was trivial.
Picking a lock is like riding a bicycle, you never forget. This lock was compromised in under three minutes even after a five year hiatus in actually using these tools.
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