idiom. Add to word list Add to word list. locked away safely: Her jewelry 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.

Typically the sweethearts' names or initials, and perhaps the date, are inscribed on the padlock, and its key is thrown away (often into a nearby river) to symbolize unbreakable love.

A house key or residential door key will have a code like "LR-2" or "SR-1" on the head. Take the key to a hardware store and ask the key maker if they know what the letter and number designation on the key signifies. Keys usually are coded by type of lock they fit and this could identify old keys.

The key serves as a security token for access to the locked area; locks are meant to only allow persons having the correct key to open it and gain access. In more complex mechanical lock/key systems, two different keys, one of which is known as the master key, serve to open the lock.