It's much easier to learn each skill in isolation, using locks specifically set up for the purpose. 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. A key that is bitted to the wrong depth in even one pin position will not operate the lock. 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. In particular note that because the pins are slightly out of alignment, as the plug is turned gently, only the pin stack that is most out of alignment actually prevents further rotation. When the energy transfers, the top pin moves up while the bottom pin slows down, and a gap is created between the two pins. The top pin of that pin stack will be trapped above the shear line, the bottom pin will fall freely, and now a new pin stack (the next most misaligned one) prevents further rotation. The top pin of the most misaligned pin stack becomes "pinched" at the shear line between the plug and the shell.

The rest is just technique -- locating and recognizing the state of each pin stack, manipulating the pins, applying torque to the plug. 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. If only serrated top pins are used, reverse picking may be successful. Two tools -- one for each function -- are used simultaneously when picking a lock. Picking tools are designed to perform one of two basic functions: manipulating pins and turning the plug. Rotation of the plug within the shell operates the locking mechanism. The basic design consists of a rotatable cylinder tube, called the plug, what is billiards linked to the underlying locking mechanism. The plug/shell border is called the shear line. Repeat until lock turns: - Locate the pin stack that's being pinched at the shear line (it resists slightly when pushed up) - Continue to push that pin stack up until its cut reaches the shear line and the plug turns slightly. If you tried to rotate the plug of such a lock without a key in the keyway, the top pin segment of each pin stack would block the plug at exactly the same number of degrees of rotation; each pin stack would contribute equally to preventing the plug from turning.

Left: The correct key lifts the pin stacks to align the cuts at the shear line. 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. Figure 1. A pin tumbler lock cylinder. Left: Cylinder face, the lock's "user interface." Note the keyway, which is cut into the plug, which in turn sits inside the shell. Right: With all of the cuts at the shear line, the plug can rotate freely within the shell. When a key is inserted into the keyway slot at the front of the plug, the pin stacks are raised within the plug and shell. See Figure 1. (In practice, the cuts are produced by stacking pin segments of particular lengths, not by actually cutting the pins; hence the term "pin stack.") With no key in the lock, all the pin stack cuts rest within the plug. See Figure 5. With the tool in the keyway, apply torque and try to turn the plug.

Figure 2. Pin tumbler lock with a correct key inserted. 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. In pool, players use the cue stick to strike a white ball called the cue ball to hit other similar balls into semicircular holes called pockets along the inner edge of the table. In addition, the level of competition may be considered since players at the top levels can be expected to be fully familiar with the rules and regulations, while relative beginners may be unfamiliar with how the rules are normally applied. Professional pool players make their money by signing up for tournaments and competing with other professional players. Of course, the more tournaments a professional player wins, the more money they will have. Similarly, if you cut pool balls into two halves, we will find them filled from the inside.