From the Super Mario Wiki
Mansion Old Clockworks

The Movements is a room inside of the Old Clockworks in Luigi's Mansion: Dark Moon. The Movements is only accessible by taking the north door inside of the Clock Tower Gate. The Movements is a large room with a metal walkway on the ground and a huge wall covered with gears of many sizes. There are several valves that Luigi can use his Poltergust on to reach the top. The numbers 0, 3, and 7, are on three of the large gears and there are two clocks on the ground that depict the time 7:30. The door on the top leads into the Belfry and the door on the south leads back into the Clock Tower Gate.

During Showtime, Luigi must make his way to the top of the Movements in order to reach the Belfry. In order to gain access, Luigi must first set the correct time on the clock in the Clock Tower Gate. The correct time is found in the Movements, which can be seen by looking through a hole nearby. On his way up, there are several spiders and gold spiders crawling on webs and there are a few Gold Bars, bill stacks, and coins inside of the gears and on the side trapped in webs.

Only during Showtime and Outlandish Interruption, when Luigi first enters the Movements, he should make his way to the window on the left. Outside the window is a ruby that Luigi can drag closer with the Poltergust 5000 so it is within reach.