How Things Work: Lock Picking

How Things Work: Lock Picking
How Things Work: Lock Picking 

By Sruthi Chintakunta
October 01, 2007

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 locks 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 

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 

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 

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 locks 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 locks 
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.

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