A rim lock, also known as a surface-mounted lock or box lock, is a type of door lock that is mounted on the surface of a door rather than being mortised into the door itself. It is one of the most common types of locks used in residential and commercial settings.

Rim locks are typically installed on the interior side of a door and consist of a lock body that houses the locking mechanism and a latch bolt. The latch bolt extends into the door jamb to keep the door securely closed. A key-operated cylinder or a thumb turn on the interior side is used to lock and unlock the door.

Rim locks are relatively simple to install and are often used on doors that have limited space or where a mortise installation is not feasible. They are commonly found on older doors, interior doors, and secondary entry points. While rim locks provide a basic level of security, they may not offer the same level of strength and tamper resistance as some other types of locks.