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How did the pound lock at Vreeswijk improve on earlier lock designs?

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View of Utrecht's Oude Gracht canal lined with historic brick buildings, arched doorways at water level, and boats moored along the canal edge in the Netherlands. — canals and inland waterways The *Oudegracht* (Old Canal), Utrecht, Netherlands.

The pound lock built at Vreeswijk in 1373 improved upon earlier designs, such as the stanches or flash locks, by introducing a controlled basin system to manage water levels.1

While earlier flash locks functioned by suddenly releasing a torrent of water to carry a vessel over a shallow area, the Vreeswijk pound lock utilized a basin enclosed by outer and inner gates. This design allowed the water level within the chamber to be controlled by alternatively winding up and lowering the gates, enabling vessels to be raised or lowered between different water levels more effectively than the previous method of towing barges over weirs with windlasses or manual labor. This innovation provided a more stable and efficient means of navigating changes in elevation along inland waterways.1