Storage Room (Luigi's Mansion: Dark Moon)
From the Super Mario Wiki
The Storage Room is a room inside of the Old Clockworks in Luigi's Mansion: Dark Moon. It is accessible by going through either of the doors on the right side of the Gear Chamber. There is a cabinet filled with tools and a Treasure Chest filled with Coins, Bills, and Gold Bars on the bottom floor. Both doors on the left take Luigi back into the Gear Chamber.
During C-5: Piece at Last, Luigi must make his way to the Storage Room to locate the rotor that a Strong Sneaker stole. Inside the Gear Chamber, Luigi can peek into the Storage Room to see the Strong Sneaker and a Greenie, but his view is cut short when a Greenie blocks the hole with a brick. After rescuing the Toad assistant and defeating a slew of Greenies and the Strong Sneaker in the Gear Chamber, Luigi can enter the Storage Room. The rotor is hidden inside a cage blocked off by some papers and posters. After removing these, Luigi must shoot the Toad into the hole of the cage so he can get the rotor.