The diagram illustrates the operation of a lock on a canal.
Overall, the operation process consists of three main stages, beginning with guiding the ship to the canal and ending with moving the ship out of the canal.
In the initial main stage, the ship, depending on its size, will be guided either by lights or signals to the selected lock on the canal. As soon as the first lock in the canal is pulled down, the ship moves toward the second lock. Subsequently, when the ship moves through the first lock, it will soon rise up in order not to let water run out of the gap between two locks.
In the next stage, people on the canal will open a hole in the second lock, which will deliver water into the gap between the two small dams. As a result, the water will move from the higher place to the lower one, and it will lift the ship up. When the water level between the second lock is exactly the same, it will be pulled down and the ship, by this way, will sail through the lock of the canal.