A lock is a mechanism that incorporates metal doors of cupboards and drawers, chests, cabinets. To prevent the can open and thus protecting its contents. This mechanism can be operated by a key metal, usually steel. At present, apart from mechanical locks, there are others such as electro-mechanical or electronic, where the key can be a plastic card or PVC. The key fit the lock on the "eye" is usually a hole in the central cylinder of the lock.