Editing Deadbolt

{{refimprove|date=July 2022}}
{{Short description|Locking mechanism}}
{{Other uses|Deadbolt (disambiguation)}}
[[File:Two holes no waiting.JPG|right|thumb|Door with two locks, one in the doorknob and a separate deadbolt]]
A '''deadbolt''' or '''deadlock''' is a type of lock morticed into a wooden door where a bolt is thrown into the door frame, using a key from either side, to secure the door. <ref>{{Cite web |title=What is a Deadlock? Everything you need to know {{!}} Locksmith Direct |url=https://www.locksmith.direct/resources/what-is-a-deadlock |access-date=2023-04-20 |website=www.locksmith.direct}}</ref> It is distinct from a [[spring bolt lock]] because a deadbolt can only be opened by a key or handle. The more common spring bolt lock uses a [[spring (device)|spring]] to hold the bolt in place, allowing retraction by applying force to the bolt itself.<ref>{{Cite web|url=https://www.oldhouseonline.com/repairs-and-how-to/how-to-repair-a-doorknob/|title=How to Repair a Doorknob - Old House Journal Magazine|date=24 October 2012}}</ref> A deadbolt can therefore make a door more resistant to entry without the correct [[key (lock)|key]], as well as make the door more resistant to [[door breaching|forced entry]].{{cn|date=August 2019}} A deadbolt is often used to complement a spring-bolt lock on an entry door to a building.

== Common types ==
A deadlock, if it is cylinder operated, may be either single cylinder or double cylinder. A '''single cylinder''' deadlock will accept a key on one side of the lock, but is operated by a twist knob on the other side. '''Double cylinder''' locks will accept a key on both sides and therefore do not require (and often do not have) any twist knob. This prevents unwanted unlocking of the door by forced access to the interior twist knob (via a nearby window, for example). Double cylinder locks are sometimes banned from areas because they can be difficult to open from the inside and violate [[fire safety]] regulations.  Some lock manufacturers also have a "lockable" knob: a key is always needed on one side (usually external), and a twist knob can be used on the other (internal), ''unless'' a button has been pressed, in which case a key is also needed on the internal side.<ref name=Abloy>{{cite web | title = Lockable Thumbturn H2X Deadbolts | url = http://www.abloy.ca/index.php?module=AxialBoutique&func=view_one_product&id=418&nav=1_99 | author = Abloy | access-date = 2011-10-22 | archive-date = 2012-04-25 | archive-url = https://web.archive.org/web/20120425083337/http://www.abloy.ca/index.php?module=AxialBoutique&func=view_one_product&id=418&nav=1_99 | url-status = dead }}</ref>

A variant of the standard deadbolt is the '''vertical deadbolt''', invented by [[Segal Lock and Hardware Company|Samuel Segal]]. Vertical deadbolts resist ''jimmying'', in which an intruder inserts a [[crowbar (tool)|crowbar]] between the door and the [[jamb]] and attempts to prise the bolt out of the door.

Other types of deadbolts include:
* Classroom-function (thumb-turn only unlocks door)
* Exit-only function (no external cylinder)
* Push-button deadbolt (mechanical or electrical)
* Single cylinder with removable thumb-turn

==Safety==
The double cylinder design raises a safety issue. In the event of a fire, occupants will be prevented from escaping through double-cylinder locked doors unless the correct key is used. This is an avoidable cause of death in house fires.{{cn|reason = One example is not often. |date=September 2022}}<ref>{{cite web | url = http://www.smh.com.au/articles/2004/06/07/1086460240897.html | title = Deadlocked doors seen as fatal in house fire  | work = [[The Sydney Morning Herald]] | first = Les | last = Kennedy | date = 2004-06-08 | access-date = 2010-11-16}}</ref> The risk can be mitigated by locking the deadlock only when there are no occupants inside the building, or leaving the key near the keyhole. Some fire departments suggest putting the key on a small nail or screw near the door at floor level, since the cleanest air is at floor level and one may be crawling to get to the exit, thus placing the key where it is easiest to find.  

Note that single cylinder dead locks (with an unlocked twist mechanism on the inside of the door) do not have this problem, and therefore are most commonly used on fire exits.  Some areas have fire safety codes that do not allow a locked exit.<ref>{{cite web |title=Hardware requirements for access and egress |url=http://www.embc.gov.bc.ca/ofc/services/guidelines/pdf/guide.pdf |publisher=Canada government |access-date=12 June 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140327145755/http://www.embc.gov.bc.ca/ofc/services/guidelines/pdf/guide.pdf |archive-date=27 March 2014 }}</ref><ref>{{cite web|title=Building Codes (p.127)|url=http://www.nyc.gov/html/dob/downloads/bldgs_code/bc27s6.pdf|publisher=New York City|access-date=12 June 2014}}</ref>

== See also ==
* [[Door security]]
* [[Lock bumping]]

==References==
{{reflist}}

{{Locksmithing}}

[[Category:Doors]]
[[Category:Locksmithing]]
[[Category:Locks (security device)]]