Introduction to the locks: The canal's locks operate on the gravity flow of each lake, including Gatun, Alajuela, and Miraflores, and are all uniform in length, width, and depth. Each set of locks is in pairs, and ships can pass through them in both directions at the same time. Each gate has two doors, 20 meters (65 feet) wide and 2 meters (6.5 feet) thick, fixed on hinges. The height of the door is 14 to 25 meters. The door leaf is driven by a motor installed in the recess of the gate wall. The opening and closing is controlled by the control tower. The water filling and discharging of the lock chamber are also controlled by the control tower. Before entering the lock, ships must pass through a protective chain stretched between the two walls of the entrance. If everything is done correctly, the protective chain will fall into the groove in the bottom of the waterway. For safety reasons, if the ship travels too fast, the ship will hit the protective chain.