It can be found attached to the electromagnet in the room next to the tram station at the top of the ladders. The green key allows the player to unlock the first floor door near the stairs that takes the player to the Fear School level. In Act Two, it is on a wall hook next to the door it unlocks. It's only required for unlocking an easier path to the third floor and train car.
It requires the magnet gun in order to be obtained. It can be found on the second floor, in a cabinet behind the painting. The blue key allows the player access to the room on the 3rd floor containing the crowbar and the platform which takes them to the Fear Supermarket level.
