a message in the closed section of a room with a barred door

There is a message in the closed section of a room with a barred door. Players have to find a remote-controlled car, put it through the bars and guide them to a key on the floor. The car has a magnet underneath and the key is on the floor. After retrieving the key, players can open the door. (Self-promotion! You can buy a part of this puzzle from Escape Room Supplier here.)