This drastically reduces the time required to exhaust the number of meaningful combinations.
Such "slops" may allow for a margin of error of plus or minus two digits, which means that trying multiples of five would be sufficient in this case. On average 1% radial rotation in either direction from the center of the true combination number to allow the fence to fall despite slight deviation, so that for a given safe it may be necessary only to try a subset of the combinations.
Nearly all combination locks allow some "slop" while entering a combination on the dial. There are also a number of tools on the market to assist safe engineers in manipulating a combination lock open in the field. A novice's opening time will be governed by these random inconsistencies, while some leading champions of this art show consistency. Manipulation is often the preferred choice in lost-combination lockouts, since it requires no repairs or damage, but can be time consuming for an operator, the specific difficulty depends on the unique wheel shapes and where the gates rest in relation to them. Wheels made from lightweight materials will reduce valuable sensory feedback, but are mainly used for improved resistance against radiographic attacks. locks were developed in response to group 2 lock manipulation. More sophisticated locks use advanced mechanics to reduce any feedback a technician could use to identify a combination. To find the combination the operator uses the lock against itself by measuring internal movements with the dial numbers. Mechanical safe locks are manipulated primarily by feel and vision, with sound helping the process occasionally.
These auto-dialer machines may take 24 hours or more to reach the correct combination, although modern devices with enhanced advanced software may successfully do this more quickly. Similar damage-free bypass can also be completed by a brute-force attack from a computerized auto-dialer or manipulation robot. Manipulation procedures can vary, but they all rely on exploiting the presence of mechanical imperfections in the lock, unlocking the safe and recovering its combination, which can then be reused to open the safe lock. It involves the manipulation of the lock in order to obtain the combination one number at a time. While manipulation of combination locks is usually performed on Group 2 locks, many Group 1 locks are susceptible to manipulation. Manipulation only requires fingers, eyes, and proper technique, though it is a skill that takes years to develop. Lock manipulation is a damage-free combination recovery method, and a well known surreptitious bypass technique. Different procedures are required to open different safes so safe-crackers need to be aware of the differences.
Different procedures may be used to crack a safe, depending on its construction.