Amnesia: Rebirth has its fair share of puzzles to solve and mysteries to unravel. An area that boasts a treasure trove of both is the Fort, which includes two fairly large buildings to explore, a half-broken tank, and a small graveyard. One of the tasks that you will have to take on in this area is fixing the elevator, which can be found in the main Headquarters building, in the center of the Fort.
After you enter the central building, you will find that most rooms are either shrouded in darkness or dimly lit. Your goal here is to find a way into the radio room, which is cordoned off by four gated walls. To get into this part of the building, you will need to fix the elevator, from which point you will be able to work through the upper and lower floors and into the radio room.
How To Fix The Elevator
At the far end of the central corridor in the Headquarters building, you will find a broken elevator that is supported by just a couple of wooden boards. To fix the elevator and ride it to the upper floor, you will need to locate two things: a winch, and a wooden board.
From the elevator, simply retrace your steps back to the central hallway until you reach a wooden ballista. At the far end of the ballista, you will be able to collect the winch, which you will need in order to operate the elevator when you come back to it.
Once you have the winch in your inventory, simply head back over to the elevator shaft and look around for a single wooden board. There should be one or two dotted around the elevator entry point. If not, then there are more scattered around the first floor. After you've retrieved one of the boards, carry it back over to the elevator shaft, and then place it down to build a bridge that connects the doors to the faraway wall.
After placing the board down, walk over to the mechanism while keeping your balance, and then equip the winch that you picked up earlier. Hover it over the mechanism until it glows white, and then attach it. From here, you will be able to operate the crank and move between the two floors. Simply wind it clockwise, and you will be taken to the second floor, from which point you will be able to push the loose cannon to smash through the floor and gain access to the radio room.
The elevator will automatically return to the first floor if you fall.