Cog Wheel Mechanism
The player has to find three Cogs, or Machine Cogs as they're known in the first Tomb Raider, in order to make the mechanism work and gain access to the Tomb of Qualopec or Anniversary version of the tomb, depending on the game.
In Tomb RaiderMachine Cogs and activate the mechanism by pulling the Wall Lever next to it. This will divert the stream to one side and shut off the waterfall, making entering the Tomb of Qualopec possible.
In Tomb Raider Anniversary
In Anniversary the mechanism is divided into three sections that are located on a mountain wall. To reach the next section, the player must have activated the previous part of the mechanism first by placing a Cog to its place. Activating the last part will lower the Floodgate, which stops the waterfall and reveals the entrance of Qualopec's Tomb.