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otheruses2|deadboltA dead bolt or dead lock (also deadbolt ), is a Lock (device)|locking mechanism distinct from a spring bolt lock because a deadbolt cannot be moved to the open position except by rotating the lock cylinder. 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. A deadbolt can therefore make a door more resistant to entry without the correct key (lock)|key .
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).cite web | url = http://www.askthebuilder.com/244_Deadbolt_Locks_-_Electronic_Locks_are_Nifty.shtml | title = Deadbolt Locks - Electronic Locks | publisher = Askthebuilder.com | accessdate = 2010-11-16 Some lock manufacturers also have a "lockable" knob: there 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 a key is also needed on the (internal) side.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 | accessdate = 2011-10-22 cite web | title = Lockable Thumbturn H2X Deadbolts | url = http://www.abloy.ca/index.php? module=AxialBoutique& func=view_one_product& id=425& nav=1_99 | author = Abloy | accessdate = 2011-10-22
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)|pry bar between the door and the jamb and attempts to pry the bolt out of the door.cite web | url = http://www.urbanfirefighter.com/index/display/article-display/7582258121/articles/urban-firefighter/volume-1/issue-2/The-Vertical-Deadbolt-Lock.html | work = Urban Firefighter | title = Vertical deadbolt
Other types of deadbolts include:
Single Cylinder with removable thumb-turn
Classroom Function (thumb-turn only unlocks door)
Exit Only Function (no external cylinder)
Push-button Deadbolt (mechanical or electrical)
Safety
This 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 often an avoidable cause of death in house fires.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 | accessdate = 2010-11-16 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 you may be crawling to get to the exit, thus placing the key where it is easiest to find.
See also
Door security
Lock bumping
References
reflist
External links
http://www.opera-italy.com/english/solenoid_bolt_external_gate.html Deadbolt in a residential use
http://www.buyschlagenow.com/shop-by-product/deadbolts/ Grade 1 Deadbolt Lock for Superior Safety
