Padlocks are portable locks with a shackle that may be passed through an opening (such as a chain link, or hasp staple) to protect against unauthorized use, theft,vandalism, or harm. 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 favour of pin-tumbler or warded mechanisms.