A combination lock is the type of lock where sequences of numbers or symbols are used to open a lock rather than a key. Often the sequence of number or symbols used is a permutation rather than a real combination and these may be entered either by entering them using a single rotation dial (which interacts with several discs or cams) or by a set of several rotating discs with inscribed numerals or symbols (which directly interact with the locking mechanism itself).
Firstly we will look at multiple dial locks and which is one of the simplest type of combination locks. These are often used for low security situations such as a bicycle lock which has several rotating discs with notches cut into them. The lock is secured by a pin that has several teeth on it which then hook into the discs that rotate around it. Thus when the discs and notches are aligned with the teeth of the pin the lock can open. Unfortunately the disadvantage of this type of lock is that it is considered to be one of the least secure types of combination locks available today.






