- Unlike locks that require a key, combination locks do not use internal tumblers. These locks can only be opened by entering a sequence of numbers determined during manufacturing. The first combination lock was designed by the mathematician Al-Jazari in 1206, though the modern form of this lock was perfected in the 1850s. Combination locks can be broken into three categories -- keypad locks, used mainly to secure doors; multiple dial locks, often seen in bicycle chains; and single dial locks, the traditional combination locks often used with lockers.
- A keypad lock is electronically controlled, where a user enters the proper series of digits and the shackle is released from within the lock, allowing the lock to open. Single dial locks involve only one dial, usually on the face of the lock. Spinning the dial to the correct numbers aligns tiny holes in a series of disks inside the lock. When the entire sequence is entered, a pin on a spring moves through the holes to release the lock.
- A multiple dial lock is hollow and tube-like, with a metal rod that enters the tube. This locks are often seen on bicycle locks, where dials are located along the tube. Spinning each dial to the correct number, lines up a notch inside the lock. When the sequence is completed, these notches allow the rod to pass through and be removed.
- A deadbolt lock is comprised of three main parts: the cylinder, the bolt and the strike plate. The cylinder is the metal face where the key is inserted to unlock the deadbolt, while the bolt is the actual metal piece that holds the door to the door frame. The strike plate is the metal piece secured to the door frame where the bolt enters, and should be secured with screws longer than one-and-a-half inches. Deadbolt locks are simple pin tumbler locks, which must be unlocked using a correctly cut key.
Combination Locks
Keypad and Single Dial
Multiple Dial
Deadbolts
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