Go to the second floor with the ladder and open the elevator door.

Enlarge the drainage outlet visible from the gap at the lower left of the wallboard inside the elevator and plug in the iron rod.

If the elevator is moved directly,  the iron rod gets caught and the elevator stops in the middle.

Enlarge the iron plate visible in the wall.
Remove the metal fixture with the coin.

Get the key.

Pull the lever and move the elevator to go to the second floor.

Enlarge the tool box placed on the floor.
Use the key.

Get the crumbled paper from inside the tool box.

Check the crumbled paper.
Get the triangular part from inside.