A master key is a special type of key that can open multiple locks, typically within a specific system. This is commonly used in places like hotels, offices, and schools, where a single key can grant access to various rooms or areas without needing individual keys for each lock. Master keys work through a specific design in the lock mechanism, allowing them to bypass standard locking systems. They are often part of a hierarchical key system, where different levels of access can be granted to different users, ensuring security while maintaining convenience.