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A Schlage brand brass body padlock.

A padlock is a portable lock used to restrict access to an area or enclosure or prevent an object from being removed from an area. Padlocks are widely used in everyday life in both low and high security installations. In popular use, padlocks are used on lockers, gates, fences, hasps, and chains to secure a wide variety of objects and areas.

Padlocks can use a variety of locking designs, but pin-tumbler and warded mechanisms are the most common. Lever padlocks were also popular at one time, but use has dwindled in most parts of the world in favor of pin-tumbler or warded mechanisms.


The earliest padlocks were from the Roman era, from 500 BC to 300 AD.

Through the last several hundred years, padlocks have become far more advanced than their earlier ancestors. Whereas many of the earlier padlocks were little more than poorly wrought designs that could be bypassed easily, today we have padlocks that incorporate high-security cylinders, restricted keyways, high-strength materials and components, and ever more advanced measures of security. For instance, some of the padlocks manufactured by Sargent and Greenleaf incorporate ceramic plates into the body of the lock, providing increased protection against attacks from drilling and freezing the lock body to extreme temperatures.

Most padlocks share a common design theme. An upside-down U-shaped shackle and a rectangular body. This common design has spread in use to indicate a secure connection on a website, with a symbol of a locked padlock in the status bar of a web browser.

Parts of a padlock

shackle, bolt
A rod made of a hardened material (typically steel) that is affixed to an object, usually a hasp, fence, or chain. The shackle is responsible for keeping the padlock connected to whatever it is attached to. This is the weakest part of the padlock in forced entry as the unprotected bolts can often be cut using bolt cutters. See bolt for more information.
The part of the padlock that surrounds the locking mechanism and most of the shackle. More secure padlocks attempt to conceal as much of the shackle as is possible to prevent various forms of forced entry. Padlocks designed in this manner are referred to as shrouded.
locking mechanism
The component that restricts the shackle until the correct key or combination is used. Modern padlocks do not interface directly with the shackle but instead use an actuator to do so. Pin-tumbler and warded locking mechanisms are the most popular on padlocks worldwide. Many padlocks use locking designs that provide a key retaining mechanism.
The portion of a padlock body that covers or conceals the shackle or bolt. Padlocks that use a shroud are referred to as "shrouded" and help defend against certain forms of destructive entry.


See also