Key

General Meaning: Safety
There is no point to having a key without some kind of lock. A key is absolutely useless unless it is used to insert in the lock. While you dream of a key, and not dream of a lock you may be warned that something of value will be lost. Being unable to unlock something (a door, a lock) sans a key is very symbolic. Keys are used in everyday metaphors: Key to my heart, or the keys to the Kingdom. Giving someone a key would indicate trust.