Master keyed padlocks open with their own key, but they also open with a master key. They allow for different levels of access, making them useful for facilities with multiple departments by restricting workers' access to one department with one key while allowing plant supervisors access to all departments with a master key. Standard shackle padlocks have a shackle that is less than 1.5" in vertical shackle clearance, while long shackle padlocks are 1.5" or more in vertical shackle clearance. Partially hidden shackle padlocks resist cutting.