A lightweight lock that attaches using a pivoting hook is called a padlock. Many high school students use lockers that can be locked with padlocks to keep their smelly gym clothes safe.
A padlock's hook or shackle is hinged so that it can fasten through an opening, clicking shut securely. Most padlocks require a key to open them, while others use a combination, a series of wheels that you turn and align to show a certain password before the padlock will open. You can use padlock as a verb, too: "Be sure to padlock the back gate when you leave!"