14 cross culverts are built into the floor of each lock. Each culvert has five well-like openings into the lock floor. The main culverts which run along the length of the locks measure 5.5 metres in diameter. Valves in these consist of two immense steel doors, weighing 10 tonnes each and moving up and down on roller bearings. Beneath the lock, the valves leading to the nest lock below it are opened.
Water drains from the upper lock and surges into the one below.
When the levels are equal the gates between the locks are opened and the ship may progress. Electric 'mules', attached to ships by lines, offer guidance and stability in the locks. Water enters or leaves through 70 openings. The reason for this large number is to spread the flow and reduce the turbulence. The steel lock gates are hollow in construction, driven by a 40-horsepower motor they open in just two minutes.