A deadbolt is a type of lock that provides enhanced security for doors. Unlike standard spring bolt locks, which can be easily manipulated, deadbolts require a key or a thumb turn to operate. This makes them more resistant to forced entry, as the bolt extends deep into the door frame when locked. There are two main types of deadbolts: single-cylinder and double-cylinder. A single-cylinder deadbolt has a keyhole on one side and a thumb turn on the other, while a double-cylinder deadbolt requires a key on both sides. This design can be beneficial for doors with glass panels, as it prevents easy access through broken glass.