Crank

Old House 1F, crawlspace under the Dilapidated Room: on the floor at the far end (where the "Mia" tape ends).

Turns the gear mechanisms that raise walkways and bridges: the one on the west side of the Dilapidated Room and the one at the end of the outside Walkway (bridge to the Outhouse, with the Crow Key). Per the wiki it also works the bridge from the Testing Area to the piers and the last bridge to the Boat House (chapter 5, Molded appear).

Do not leave it in the box until you reach the Boat House.