A padlock is a portable lock with a U-shaped metal bar called a shackle that clicks into the lock's body. Unlike locks built into doors, a padlock can be carried around and used wherever you need it. You loop the shackle through a hasp on a shed door, through the links of a chain, or through the holes in a locker, then snap it closed.

Padlocks have been used for centuries to protect belongings. In schools, students use combination padlocks on their lockers, spinning the dial to the right sequence of numbers to open them. Cyclists use padlocks to secure their bikes to racks. Warehouses use heavy-duty padlocks on storage containers.

To open a padlock, you need either the right key or the correct combination. The beauty of a padlock is its flexibility: one good padlock can protect your gym locker today, your toolbox tomorrow, and your suitcase while you travel.