Beyond figuring out what type of brand you have, there are greater variations in locks. In order to determine all of the information about your particular lock, there are several things you need to know. Those things include an overview of the types of inspections that you can perform, information on different types of locks, and how to test whether you are correct in your diagnosis. Without the right classification, you will know next to nothing about the lock’s mechanical principles.
An external inspection can be done at any time and does not require any tools. Simply observe the lock, the key, and how the lock and key interact. Pay attention to the bitting on the key (the serrations/grooves), the shape, and the size. For the keyway, analyze how open it is, the size, and the shape. Compare your visual data to the information in the “The Variety of Lock Types” section of this article.
An internal inspection requires some knowledge of the inner workings of locks, and some tools. You will be probing the lock with a lock pick, or similar spring steel implement that will fit in the keyway. You may also need a tension wrench, which you will use to apply torque to the lock. Adding tension will give more feedback from the lock to your tools, and ultimately make it easier to feel what is happening in the lock. Achieving tension will also allow you to pick the lock.
Taking the lock apart requires the most experience out of all of the inspection methods. It may also require the use of specific tools. Without the proper knowledge, you may not be able to reassemble the lock once you have broken it down. Keep in mind as well that not all locks can be reassembled. The process of opening a lock to understand it may compromise the lock irrevocably. That being said, once it is open you can examine the internal locking mechanisms.
1. Standard Pin Tumbler lock
- Most common for North American homes.
- Keys have bitting on one edge and are smooth on the other.
- Keys can only be inserted one way.
- Most commonly will have 5 pin stacks, but some popular models might go as high as 7, or as low as 4.
- Each pin stack will contain a key pin, driver pin, and a spring, which interact in that order.
- Key pins are cut to different sizes and touch the key directly.
- Driver pins are a standard size, and rest between the springs and key pins.
- Keyways will be rectangular with warding that gives them a maze-type appearance.
2. Wafer Lock
- Most commonly used on older model automobiles.
- Keys have bitting on both edges.
- Keys can be inserted two ways, and there is no upside down.
- Locks use wafers instead of pins, which need to be either depressed or elevated to open.
- Some wafer locks are one-sided, like those used in filing cabinets and lockboxes.
- Keyways are more open and more accurately resemble a standard rectangle.
3. Barrel Lock
- Most commonly used for electrical meter locks in North America.
- The keys resemble a screw with a handle and often have a plastic or rubber cap.
- The handle acts as a plunger that extends metal probes on the key.
- The probes grip the core and retract the locking dogs.
- The core acts as the lock bolt and must be removed to open the lock.
- Keyways are small and circular.
- There is nothing to feel inside the keyway.
4. Disk Detainer Lock
- Found most often on padlocks, varying in quality, but associated with high security.
- Keys have grooves that travel along all sides of the key.
- The disks in the lock must be rotated so that cuts on the disks (known as gates), line up with a sidebar.
- Keyways are most often rectangular and very open, much like a wafer lock.
5. Tubular Lock
- Used for a variety of devices such as cabinets, automated teller machines (ATMs), vending machines, bike locks, etc.
- Keys are circular with grooves on the outside and a hollowed out middle.
- Keys have a notch to tension the lock, and to display the one way the key can be inserted.
- This is technically a pin tumbler lock, but the pin stacks are placed in a circle pointing at the user.
- Keyways look like the power sign on a computer (a ring with an intersecting rectangle).
6. Slider Lock
- Most commonly used on newer automobiles.
- Keys have a snake-looking pattern on one or two sides.
- If two-sided, the key can be inserted two ways.
- The winding trail on the key moves small internal components called sliders to specific heights.
- Keyways are very open and rectangular.
7. Lever Lock
- Commonly used in commercial and law enforcement settings.
- Keys will have a large rectangular end on a cylinder-shaped length of metal.
- Keys may have a hole in the center that lines up with a cylinder in the keyway.
- Bitting on these keys are deep and rectangular in shape.
- Levers will be flat pieces of metal stacked together, which raise to open the lock.
- Because of the size of the levers these are often found in mortise lock bodies.
- Keyways look like the keyholes in cartoons, with a round hole on top of a rectangular hole.
8. Warded Lock
- Found in some padlocks, and older homes.
- Keys have deep rectangular grooves.
- Older style warded locks will have a hole that fits a cylinder-shaped piece of metal to orient it in the lock.
- Newer versions, like those on the Master 22 are double-sided with no orientation cut.
- These locks have warding on the inside that must be navigated around to access the internal components.
- Older style keyways will have a similar look to lever lock keyholes.
- Newer keyways are very open and wide, so you can look straight down and see that there are no internal mechanisms.
There are, of course, all kinds of hybrids and variations in locks, but those listed above are the most common. Older relics may use screw key systems, and other countries and regions may have different hybrid standardizations.
With your initial inspection and your new-found knowledge of the different types of locks, this should allow you to gain new insight by simply using the lock. Insert the key and open the lock. Re-lock the lock and do this process again, slower. As you press the key inside the lock try to feel what is happening in the lock. By slowing down the process of opening the lock you will get a better idea of the movement of the internal parts.
Before using a probe on the lock, you should use a spray lubricant in the keyway. You want to stay away from oil based sprays as these will jam up the internal components of the lock. Use something akin to graphite, but be careful about staining. As you probe to see what is moving and try and feel how it is moving. How much surface area you have for manipulation will tell you if it is a pin or a lever. If you can rotate the components then it is most likely a disk detainer. How the internals move will give you a lot of information. Without tension, all of the parts should be free moving, with no binding taking place.
Actually picking the lock is the ultimate test of your understanding. This will allow you to find out the most you could learn about the lock without taking it apart. By trying to defeat the security of a lock, you will run up against all of its security features. A knowledgeable locksmith or engineer will be able to feel the presence of false gates, and security pins. If the lock is successfully picked with skill and not luck, most general knowledge can be ascertained. For specific information, you will need to take the lock apart.
By inspecting the lock, knowing about the different kinds, and further testing, you can begin to understand these unique and complex mechanisms. Be aware that old and malfunctioning locks may give false signs of having another lock’s characteristics, and customized locks may have purposefully deceptive indications. Approach disassembly with prior knowledge of the lock, and with an understanding that the lock may be compromised by being opened. Do not continually pick or probe a lock that is in use, as this may result in damage that leaves the device inoperable. You should also never pick locks that you do not own, or have not been given permission from the owner to pick.