Key
From Conservapedia
Saints Peter and Paul. Peter is identified by a key, Paul by a sword.
For the music term, please see key (music)
A Key is a shaped piece of metal used to lock or unlock a lock. Typically a key for one lock will not work in any other lock, but a master key will open a series of locks that also have their own individual keys.
In religious art, St Peter is often depicted holding a key, symbolising his role as the keeper of the gates of Heaven.