Editing Lock (water navigation) (section)

==History and development==
===Pound lock===
[[File:Replica sluis in Botterbeek P3260262.JPG|thumb|Model of early river pound lock, constructed in Lankheet water park, Netherlands]]
[[File:Monkey-Marsh-lock-by-John-Lloyd.jpg|thumb|The turf-sided [[Monkey Marsh Lock]] on the Kennet & Avon Canal at [[Thatcham]]]]

The natural extension of the [[flash lock]], or staunch, was to provide an upper gate (or pair of gates) to form an intermediate "pound" which was all that need be emptied when a boat passed through. This type of lock, called a pound lock, was first used in medieval China during the [[Song dynasty]] (960–1279 CE). The Songshi or History of the Song Dynasty, volume 307, biography 66, records how Qiao Weiyue, a high-ranking tax administrator, was frustrated at the frequent losses incurred when his grain barges were wrecked on the [[Xi River|West River]] near [[Huai'an]] in [[Jiangsu]]. The soldiers at one double slipway, he discovered, had plotted with bandits to wreck heavy imperial barges so that they could steal the spilled grain. <ref name="needham volume 4 part 3 352"/>

In 984 Qiao installed a pair of sluice-gates two hundred and fifty feet apart, the entire structure roofed over like a building. By siting two staunch gates so close to one another, Qiao had created a short stretch of canal, effectively a pound-lock, filled from the canal above by raising individual wooden baulks in the top gate and emptied into the canal below by lowering baulks in the top gate and raising ones in the lower.<ref name="needham volume 4 part 3 351"/>

Pound locks were used in late 14th century Europe. A pound lock was built in 1373 at [[Vreeswijk]], Netherlands, and serviced numerous ships in a large basin. Another one was built in 1396 at [[Damme]] near [[Bruges]], Belgium. The [[Italy|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.<ref name="needham volume 4 part 3 358">Needham, Volume 4, Part 3, 358.</ref><ref name="needham volume 4 part 3 357"/>

===Turf-sided lock===
A turf-sided lock is an early form of canal lock design that uses earth banks to form the lock chamber, subsequently attracting grasses and other vegetation, instead of the now more familiar and widespread brick, stone, or concrete lock wall constructions. This early lock design was most often used on river navigations in the early 18th century before the advent of canals in Britain. The sides of the turf-lock are sloping so, when full, the lock is quite wide. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. On British canals and waterways most turf-sided locks have been subsequently rebuilt in brick or stone, and so only a few good examples survive, such as at [[Garston Lock]], and [[Monkey Marsh Lock]], on the [[Kennet and Avon Canal]].<ref>{{cite web|url=http://www.waterscape.com/services-directory/1418/monkey-marsh-lock|title=British Waterways 'Waterscape' website|access-date=11 January 2011|url-status=dead|archive-url=https://web.archive.org/web/20120403023653/http://www.waterscape.com/services-directory/1418/monkey-marsh-lock|archive-date=3 April 2012}}</ref>