I shall mention two, though one is sufficient for a master-key to them all.
She had provided herself with a master-key which opened all the doors.
This is the State secret; this is the master-key to the whole policy.
Analysis: The master-key is the key that opens all the doors of the asylum.
Love is the master-key that opens every ward of the heart of man.
Quickly I shot the bolts and unlocked it with my master-key.
One fiery rush and the master-key of all these locked doors might be in our keeping.
The mystery of Sex is, surely, Master-key to all the other mysteries of the Cosmos.
For a second only he hesitated, then swiftly fitted the master-key and opened the door.
I had Effingham produce his master-key, and the door was opened.