Thanks, everyone. This one has been a challenge because of all the activity. And the low, direct lighting, a result of the very early morning hour and my desire to include the setting moon (not visible in this crop).
Ulco, I think you're right about the rope. If I remember correctly it's two inches in diameter, but it appears larger than that. Aesthetically it would be a good idea to make it less hefty. An easy fix.
Each of the lock gates has a butterfly valve that can be opened to drain the lock chamber so the gates can be opened. The valves are out of sight here (they are under water, even when the water level in the chamber is lowered), but if you look closely you can see the wrought-iron stems and handles of the "keys" used to open them, protruding from the tops of the gates. The technology was crude and demanded a lot of muscle power, but it worked.