Lock picks work by pushing the pins in a lock-up one at a time until they all line up with the shear line so the lock core can rotate. This is done by applying rotation force to the core of the lock while pushing up the pins one at a time with a lock pick in order to hold them in place. Once all pins are in the correct position the lock will open.
In the movies, they make lock picking look so easy. A character kneels in front of a door. Pulls out a set of tools. Inserts them. Fiddles the tools, and not surprisingly, the door creaks open.
Simultaneously, apply rotational tension to the cylinder as the key pins are individually lifted and set at the shear line of the bible. That’s what lock picking is doing as it attempts to mimic the mechanics of the proper key.
Obviously, we have jumped the lock-picking gun and gotten ahead of ourselves. We need to examine the inner workings of a lock and key.
When people imagine a padlock, I believe the first thing to come to mind is a standard Master Lock, something definitely not on the LockPicking Lawyer’s highest-reviewed locks. These are pin tumbler locks and the most common type of padlock.
These locks appear simple and work efficiently while they have multiple moving parts that the user rarely sees.
How Does a Lock Work?
Insert the correct key and turn. Simple as that. The mechanics, however, are so much more.
Parts of a Padlock
- Case: The case is the body of the lock and holds everything in place.
- Shackle: The shackle is the piece that is released upon the lock being “opened”.
- Plug: The plug is the cylinder with the keyway and has the cam on the back, opposite the keyway. The plug is the part of the lock that rotates when the correct key is inserted and turned.
- Pin Chambers: Within the plug, we find multiple holes leading into vertical shafts in a “straight” line at the top of the keyway into the case. Some locks have a “bible” which is a rectangular metal box on top of the plug that contains these vertical shafts.
The two pins and spring are found in each vertical shaft. These vertical shafts are commonly called “pin chambers”.
Some locks may include a hidden vertical shaft with a pin in the back of the plug that is not accessible, in which it holds the plug within the case or body of the key, thus preventing it from being pulled out. The pin sits in a groove as the plug is rotated with the key.
In each of the pin chambers, from the top of the chamber to the bottom, there is a spring, followed by two pins. Additionally, there is a ledge where the pins sit when not engaged.
- Pins: These pins are the reason why the correct key is required to rotate the plug, thus opening the lock. The pins serve as an obstruction preventing the plug from rotating to the open position.
Pins are small cylindrical pieces of metal. Standard pins are smooth on all sides. There are a number of other pin types, including spools, serrated, and mushroom, that make locks more difficult to pick open.
The set of pins that engage directly with the key are called the key pins.
The pins that rest on the key pins and beneath the springs are called the driver pins. The driver pins may be reshaped by the lock designer into various types in order to make lock picking difficult. These non-standard pins are called security pins and will be discussed in a future article.
When the proper key is inserted into the keyway and engages each of the pin chambers, the driver pins are lifted by the key, and the key pins are just above the shear line.
- Sheer line: The sheer line is where the plug and case or bible meet.
By default, one or more of the pins may be obstructing the shear line, thus preventing the rotation of the plug.
- Cam: The cam is the end of the plug that retracts the locking lugs to release the shackle, opening the lock. The cam in a basic pin tumbler lock is cupped by two spring-loaded latches.
In their neutral position, the latches are pushed into the notches of the shackle by the springs. A spring below the shackle is pushing the shackle up. With the shackle free of the latches, the spring pushes the shackle free of the lock body.
This great video by The Engineering Mindset, wonderfully shows the mechanics of the cam ledges.
As the cam is rotated, the turning motion pushes each of the latches inward and opposite the direction, their springs are pushing.
Clearing the shackle of the latches springs the shackle free and open.
Lock and Key Recap
Let’s quickly recap the basic flow of a lock and key:
The proper key pushes the pins to their positions aligning with the shear line. As you can see in the diagram above.
The key then freely rotates the plug.
The cam forces the latches into the lock body.
The latches disengage from the shackle.
The shackle springs the shackle free of the lock body.
Those are the basics of the pin tumbler lock, but now we need to figure out how to open it using lock picks.
How do Lock Picks Work?
Lock picks are used to push the key and driver pins up into their correct positions inside a lock, one at a time while turning the core of the lock to hold them in place.
This mimics what a key would do inside the lock, being that a key will push all the pins up to their correct positions all at once allowing the core of the lock to turn.
As lockpickers, we use these flaws to our advantage.
There are plenty of flaws when it comes to locks but we are going to focus on those that allow us to pick a lock.
As described earlier, the “straight” line of pin chambers containing the pins is the weakness we are aiming to exploit when picking a lock.
The minute imperfections of poor machining cause these imperfections.
High-quality locks are constructed with improved machinery with the goal of minimizing the flaws.
Low-quality locks may have exaggerated errors in the pin chamber positions thus allowing for easier lock picking.
Ironically, some poorly built cheap locks may be challenging due to their poor construction.
The Mechanics of Lock Picking
The smallest errors of pin chamber alignment allow us as lock picks to identify the binding pin(s).
When lock picking, as the plug is rotated with the tension tool there is a pin that is the initial obstruction. The other pins will likely move more freely.
Setting the binding pin means pushing the driver pin above the shear line while the key pin remains below the shear line.
Upon setting the binding pin, we may move along the pins and test the others by feel to identify the next binding pin.
With all of the driver pins set above the shear line and the key pins freely below the shear line, the plug will rotate to the open position.
As a lock picker repeatedly picks a lock they will get familiar with it’s internal workings.
Frequently, you may hear lock pickers use the words “binding order”.
The binding order of a lock is the flow best suited for setting the pins of a specific lock.
This makes for easy picking of a specific lock, when one knows the order of the pins that are to be set. In order to avoid this “problem”, lock sport hobbyist will get multiple locks of the same lock model and work their way through these, including the legend himself, in order to approach each lock as if for the first time.
Given the right tools, time and skill, any lock can be picked.
In this article, we described the method and mechanics utilized to pick open a padlock by taking advantage of manufacturing flaws.
In future articles we will identify other methods of picking a padlock as well as the approach to those other lock picks out there.