A thumb turn lock is a type of locking mechanism commonly used on doors. It features a rotating cylinder that can be turned with a thumb, allowing for easy locking and unlocking from the inside without needing a key. This design is often found in residential settings, providing convenience and quick access. These locks are typically paired with a standard key lock on the outside, ensuring security while allowing occupants to exit quickly in case of an emergency. Thumb turn locks are popular for their simplicity and effectiveness, making them a practical choice for many homeowners.