locked away safely: Her jewellery is securely under lock and key at the bank. If a person, especially a criminal, is under lock and key, they are being kept in a place from which they cannot escape, usually a prison.
What is the meaning of the Cross Keys?
The Crossed Keys Symbol. Along with the city arms, the crossed keys is one of the most common symbols to be found on the streets of York. The keys in question represent the keys to heaven, as held by St Peter, its traditional gatekeeper.