Abstract: Apparatus and method for a secure multi-level key system. A multi-level key system utilizes ribs of known width upon the higher level keys to properly displace obstruction pins corresponding to selected locking pins of the lock housing. A two-part cylinder pin is utilized in order that a higher level key may equalize the spring-biased locking pin with a shallower groove than is necessary for a subordinate key to equalize the same locking pin. The obstruction pins sense the presence or absence of the ribs associated with the high order keys. Subordinate keys, lacking ribs, depend on the additional displacement of the cylinder pin to properly position the obstruction pins to unlock the lock. Creation of a higher order key requires a two-step process of reducing the depth of the groove corresponding to a given cylinder pin of the lock as well as building up the ribs required to offset the obstruction pins associated with the same cylinder pin of the lock.