The Key is a important item on FNaF World. It is obtainable right after beating Porkpatch.
Once you walk to the Key, it will stay under the name of the Location forever, and it will be usable forever. It can unlock reddish-pink walls around the world that will lead to Guardians and buttons that will unlock a path on Pinwheel Circus. However, if the player got all Clocks, on a spot on Chipper's Woods that is close to Lilygear lake, instead of having a Guardian, there will be a portal that will trigger the Clock Ending.