With the upper gates open and the lower closed, a boat enters the lock while the water level is high. The upper gates are then closed and the lower wickets opened to lower the water level as a boat approaches traveling upstream. Once the levels have equalized, the lower gates are opened to let the first boat out, and the upstream-bound boat enters the lock. After it is inside, the lower gates are closed and the upper wickets opened to fill the lock. When the water levels equalize again, the upper gate opens and the boat continues upstream.