page_title: Lock (water navigation)
section_title: Steel gates
hierarchical_section_title: Lock (water navigation) / Variations / Steel gates
caption_attribution_description: English: Lock 10 on the Chesapeake and Ohio Canal, part of 7 Locks
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: Steel gates and/or balance beams are frequently used nowadays, although all-wooden versions are still fitted where appropriate.
  Swinging gates. Even very large steel-gated locks still can use essentially the same swinging gate design as small 250-year-old locks on the English canals. On English canals, steel gates usually have wooden mitre posts as this gives a better seal.
  Sliding gates. Some low-head locks use sliding steel gates (see Kiel Canal). The sliding gates of the Nieuwe Meersluis in Amsterdam double as roadways.
  Caisson gates. A kind of sliding gate that is hollow and can float. It can be constructed to withstand high heads.
  Guillotine gates. Some locks have vertically moving steel gates – these are quite common on river navigations in East Anglia. Sometimes just one of the pairs of swinging gates is replaced by a guillotine: for instance at Salterhebble Locks, where space to swing the balance beams of bottom gates of the lowest lock was restricted by bridge widening. On the River Nene most locks have this arrangement as in time of flood the top mitre gates are chained open and the bottom guillotines lifted so that the lock chamber acts as an overflow sluice. Guillotine gates are also used on the downstream side of larger locks such as the 23m Bollène lock on the River Rhône, the aperture being large enough for a boat to travel under it.
  Vertically rotating gates (American usage: Drop gates)  are gates which, when open, lie flat on the canal bed and which close by lifting (London Flood Barrier). Some of these were installed on the Chesapeake and Ohio Canal in the congested 7 Locks area since they could be operated by one man and also could speed up traffic.
  Rotating-sector gates. Some of these work very like traditional swinging gates, but with each gate in the form of a sector of a cylinder. They close by rotating out from the lock wall and meeting in the centre of the chamber. Water is let in or out by opening the gates slightly: there may be no paddles or other lock gear. The lock at Limehouse Basin, which gives access to the River Thames, is an example. A dramatically large one can be seen at the Maeslantkering (huge flood gates) near Rotterdam. There is a different type at the sea lock on the Ribble Link: this is a rising sector gate, which has a horizontal axis: the gate drops to the bed of the river to allow boats to pass.
caption: Example of a lock with a drop gate (Lock 10) on the Chesapeake and Ohio Canal
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