A bump key is a specially crafted key that can open pin tumbler locks, which are commonly used in doors. It is designed to fit into the lock and, when struck or "bumped," causes the pins inside the lock to jump, allowing the lock to turn and open. This technique exploits the mechanical design of the lock, making it a potential security risk. While bump keys can be used for legitimate purposes, such as locksmithing or gaining access to one's own property, they are also associated with criminal activity. Awareness of bump keys has led to discussions about improving lock security and exploring alternatives like smart locks or more complex locking mechanisms.