Editing Lock (water navigation) (section)

=== Doubled, paired or twinned locks ===
[[File:Lockport bartlett color.jpg|thumb|Doubled locks. Left lock has boat in it, right lock (center of drawing) is empty. This is on the Erie Canal at Lockport.]]
Locks can be built side by side on the same waterway. This is variously called ''doubling'', ''pairing'', or ''twinning''. The [[Panama Canal]] has three sets of double locks. Doubling gives advantages in speed, avoiding hold-ups at busy times and increasing the chance of a boat finding a lock set in its favour. There can also be water savings: the locks may be of different sizes, so that a small boat does not need to empty a large lock; or each lock may be able to act as a side pond (water-saving basin) for the other. In this latter case, the word used is usually "twinned": here indicating the possibility of saving water by synchronising the operation of the chambers so that some water from the emptying chamber helps to fill the other. This facility has long been withdrawn on the English canals, although the disused paddle gear can sometimes be seen, as at [[Hillmorton]] on the [[Oxford Canal]]. Elsewhere they are still in use; a pair of twinned locks was opened in 2014 on the [[Dortmund–Ems Canal]] near [[Münster]], Germany.<ref>{{cite web|url=http://www.wna-datteln.wsv.de/projekt_wna/dek_suedstrecke/Schleusen/Zwillingsschleuse_Muenster/|title=Zwillingsschleuse Münster|language=de}}</ref>

The [[Soo Locks]] at Sault Ste. Marie include the two American locks, the MacArthur Lock which is {{cvt|800|ft|m}} long, {{cvt|80|ft|m}} wide, and {{cvt|29.5|ft|m}} deep and the Poe lock which is {{cvt|1200|ft|m}} long, {{cvt|110|ft|m}} wide, and {{cvt|32|ft|m}} deep, and the Canadian lock which is {{cvt|77|m|sp=us}} long, {{cvt|15.4|m|sp=us}} wide and {{cvt|13.5|m|sp=us}} deep. The MacArthur is used for ships which fit the smaller locks on the [[Welland Canal]], while the Poe lock accommodates the larger [[Lake freighter|lakers]] that can operate only on the upper four [[Great Lakes]]. The Canadian lock is used for recreational and tour boats.

The staircase at [[Lockport (city), New York|Lockport, New York]], was also a doubled set of locks. Five twinned locks allowed east- and west-bound boats to climb or descend the {{convert|60|ft|m}} [[Niagara Escarpment]], a considerable engineering feat in the nineteenth century. While Lockport today has two large steel locks, half of the old twin stair acts as an emergency spillway and can still be seen, with the original lock gates having been restored in early 2016.<ref>{{cite web|url=https://www.governor.ny.gov/news/governor-cuomo-announces-funding-restoration-lockport-locks|title=Governor Cuomo Announces Funding For Restoration of Lockport Locks|date=17 August 2015|website=ny.gov|access-date=21 September 2018}}</ref>