A key that is bitted to the wrong depth in even one pin position will not operate the lock. The height (or cut depth) of a key under each pin stack position is called its bitting; the bitting of a key is the "secret" needed to open a lock. These imperfections are very small -- as little as .0001 inches in some cases -- but they are what allow us to manipulate ("pick") locks open without using the correct key. If just one pin sets at the "other" shear line, the lock will not open even though all the pin stacks are picked. Right: With all of the cuts at the shear line, what is billiards the plug can rotate freely within the shell. The top pin of the most misaligned pin stack becomes "pinched" at the shear line between the plug and the shell. If this pin stack is slowly pushed up with torque applied to the plug, eventually its cut will reach the shear line and the plug will turn a bit more. Left: Cylinder face, the lock's "user interface." Note the keyway, which is cut into the plug, which in turn sits inside the shell. The basic design consists of a rotatable cylinder tube, called the plug, linked to the underlying locking mechanism.

The plug/shell border is called the shear line. Note the border between the plug and shell, which forms the shear line, and the cuts in each pin stack resting within the plug. Pin tumbler lock picking consists of raising the cuts on each pin stack to the shear line, one by one, until the plug turns freely. The basic skills of pin tumbler lock picking include selecting the proper tools, manipulating pins through the keyway, applying torque, and recognizing the state of each pin. The shape of the tip is the most obvious difference between picking tools, with hooks, half-diamond, ball, double ball, wave, sawtooth and other styles available. Other differences between picks, aside from the shape of the tip, are the material, finish, width and thickness of the tang shaft, and the shape and material of the handle. Picking tools are designed to perform one of two basic functions: manipulating pins and turning the plug.

Avoid so-called "feather-touch" and spring-loaded torque tools altogether. If the torque tool is too thin, it will tend to be "springy" and will absorb much of the fine movement and control needed to successfully pick better quality locks. Both the pick and the torque tool also amplify and transmit feedback about the state of the lock back to their user. The rest is just technique -- locating and recognizing the state of each pin stack, manipulating the pins, applying torque to the plug. Note that excessive raking with any of these techniques will tend to overset pins, so be prepared to release torque and start over from time to time. The pick must be strong enough to resist bending or breaking while lifting pins, yet the shaft must be small and thin enough to maneuver freely around the keyway without disturbing other pins. See Figure 2. The plug will be blocked from rotating if any pin stack is lifted either not far enough (with the cut still in the plug below the shear line) or too far (with the cut pushed above the shear line and into the shell); to rotate, all pin stacks must have a cut at the shear line.

In general, the torque tool should be as thick as possible while still fitting in the keyway, and of a width sufficient to provide good control but without interfering with the picking tool's access to the pins. The traditional torque tool is made from stiff, flat spring steel, bent at a 90 degree angle to provide a small blade that fits in the keyway and a long handle to which torque is applied. A few pin tumbler lock products orient the key horizontally in the keyway and use a flat key bitted with variable-depth holes ("dimples") rather than the cuts used for the familiar "sawtooth" key. If serrated bottom pins are used as well (as they are in, e.g., certain American brand padlocks), snap guns, bump keys, or sawtooth raking are likely the only picking techniques that will succeed, especially for the novice. A variety of picking tools are available through most locksmith supply distributors. Good tools are important, to be sure, but once a few basic tools are available the student of lock picking is usually better off investing in new locks on which to practice rather than in new picking tools. The disks are connected in sequence via interlocking cams such that one rotation of the dial engages the first disk, two rotations engage the second, and so on.