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A dead bolt, deadbolt or dead lock is a locking mechanism distinct from a spring bolt lock because a deadbolt cannot be moved to the open position except by rotating the lock cylinder with the key. The more common spring bolt lock uses a 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. 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.〔(【引用サイトリンク】 url = http://www.abloy.ca/index.php?module=AxialBoutique&func=view_one_product&id=418&nav=1_99 )〕〔(【引用サイトリンク】 url = http://www.abloy.ca/index.php?module=AxialBoutique&func=view_one_product&id=425&nav=1_99 )〕 A variant of the standard deadbolt is the vertical deadbolt, invented by Samuel Segal. Vertical deadbolts resist ''jimmying'', in which an intruder inserts a pry bar between the door and the jamb and attempts to pry 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 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dead bolt」の詳細全文を読む スポンサード リンク
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