A lock is a mechanical or electronic fastening device that is released by a physical object such as key or secret information such as a key code or password, or combination of more than one of these. A combination lock is a type of lock in which a sequence of numbers or symbols is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed numerals which directly interact with locking mechanism. Padlocks are portable locks used to defend against theft, vandalism, sabotage, unauthorized use, and even harm. They are designed to protect against some degree of forced and surreptitious entry.