How Things Work: Lock Picking
Through the delicate handling of small, metal parts, thieves and detectives can find their way into buildings without using a key.
Lock picking involves the modification of a lock’s internal components. Picking a lock is like cracking a secret code.
“Cylindrical locks” are one of the more common types of locks that are found on doors. For cylindrical locks, keys are used to turn a plug inside the lock. A plug is a small cylinder that is encased in a housing.
The rotation of the plug turns a cam. A cam is like a miniature arm that extends off of the plug. When the cam rotates, it pulls on the bolt, and the door opens.
The types of cylindrical locks found on doors include the pin-and-tumbler, wafer-tumbler, and tubular designs. Pin-and-tumbler locks have a single row of pins lined up inside the lock. The pins are grouped into pairs, each of which consists of a bottom and top pin. Each of these pairs is embedded in a shaft that goes through the cylinder plug.
These pairs of pins are kept in their positions by springs that are connected to the top pin. In other words, the spring pushes the top pin downward by applying a force, causing the top pins to be partly located inside the plug and partly inside the housing that surrounds the plug.
The bottom pins, on the other hand, are pushed down to the very the bottom of the hollow shaft so that they are located entirely within the plug.
This orientation of the pins prevents the top and bottom pins from separating, and so, the lock cannot turn.
When the correct key is inserted into the keyhole, these pairs of pins are lifted upward so that the top pins are located entirely in the housing. When the key turns, the top and bottom pins separate, and the door unlocks.
It takes two tools — picks and tension wrenches — to pick cylindrical rocks. Picks are thin strips of metal that are used to modify the positions of the lock’s pins. Tension wrenches, on the other hand, are L-shaped tools that allow lock-pickers to hold pins in place as the door is unlocked.
When the tension wrench is inserted into the lock and turned, the connection between the upper pin and the lower pin becomes disoriented.
The next step is to start raising the pins by inserting the pick completely into the lock. The objective is to lift the pins so that all of the top pins are located entirely in the housing.
The top pins make a clicking sound when they move to the housing, and the tension wrench helps maintain their positions.
You have to make all the upper pins fall into position for the door to be unlocked, meaning that the pins have to rest at the shear line. The shear line is the point at which the top pins are located entirely in the housing.
Another method for picking locks is called raking. Raking serves the same purpose of making the upper pins and lower pins fall into the right position so that the wrench can be used to turn the cylindrical plug.
In raking, however, the pick is wider. Also, the pick is fully inserted into the lock and then pulled out quickly. The hope is that all of the pins fall into their proper positions.
Locksmiths will frequently first use raking and then pick the remaining pins one by one more delicately.
Wafer-tumbler locks are similar in design to the pin-and-tumbler locks, except that they use disks instead of pins. The above-mentioned method can be used to pick wafer-tumbler locks, and they even have wider keyholes than pin-and-tumbler locks.
Some wafer-tumblers contain single wafers instead of pairs. These wafers are fixed in the lock using spring, and they attach to the lock’s housing. A key pulls these wafers completely into the plug, allowing the plug to turn.
Tubular locks, on the other hand, have rows of pins that line the inner surface of the plug. These locks are more secure than pin-and-tumbler locks and wafer-tumbler locks because they are so difficult to successfully pick.
One alternative to conventional methods of lock picking is to use an electric pick gun. A pick gun uses the raking concept to open the lock by vibrating inside the luck and pushing the pins up.
Thus, a lock gun may or may not be able to open the lock, as there is always an uncertainty as to whether all the upper pins have been lined at the shear line.
In addition to a steady hand, locksmiths need a sharp sense of hearing, an attribute that lock pickers also must have. Lock pickers must listen for the ‘click’ that occurs when pins are put in an unlocked position, which indicates that the lock has been correctly modified.