Abstract: Mechanical digital lock operable through a series of mechanical operations actuated by the depression of digital keys comprises an intellectual combination of essential mechanisms including a plurality of keys, digital selectors, identifiers, locking means and automatic resets. The lock cannot be opened unless the predetermined digitals are sequentially depressed. Once the lock is opened, it is automatically reset. A change of combination of digitals can easily be manually effected without any tool. With its novel structure, it is highly reliable.