page_title: Lock (water navigation)
section_title: Pound lock
hierarchical_section_title: Lock (water navigation) / Pound lock
caption_attribution_description: English: Kapeenkoski Lock of Keitele–Päijänne canal in Äänekoski, Finland Suomi: Keiteleen kanavan Kapeenkosken sulku Äänekoskella
context_page_description: A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself that rises and falls.
  Locks are used to make a river more easily navigable, or to allow a canal to cross land that is not level. Later canals used more and larger locks to allow a more direct route to be taken.
  Since 2016, the largest lock worldwide is the Kieldrecht Lock in the Port of Antwerp, Belgium.
context_section_description: A pound lock is a type of lock that is used almost exclusively nowadays on canals and rivers. A pound lock has a chamber with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock.
  Pound locks were first used in medieval China during the Song Dynasty (960–1279 AD), having been pioneered by the Song politician and naval engineer Qiao Weiyue in 984. They replaced earlier double slipways that had caused trouble and are mentioned by the Chinese polymath Shen Kuo (1031–1095) in his book Dream Pool Essays (published in 1088), and fully described in the Chinese historical text Song Shi (compiled in 1345):
  The distance between the two locks was rather more than 50 paces, and the whole space was covered with a great roof like a shed. The gates were 'hanging gates'; when they were closed the water accumulated like a tide until the required level was reached, and then when the time came it was allowed to flow out.
  The water level could differ by 4 feet (1.2 m) or 5 feet (1.5 m) at each lock and in the Grand Canal the level was raised in this way by 138 feet (42 m).
  In medieval Europe a sort of pound lock was built in 1373 at Vreeswijk, Netherlands. This pound lock serviced many ships at once in a large basin. Yet the first true pound lock was built in 1396 at Damme near Bruges, Belgium. The Italian Bertola da Novate (c. 1410–1475) constructed 18 pound locks on the Naviglio di Bereguardo (part of the Milan canal system sponsored by Francesco Sforza) between 1452 and 1458.
caption: A pound lock on the Keitele–Päijänne Canal at Äänekoski in Central Finland
exif: {}