A door closer is a mechanical device that automatically closes a door after it has been opened. It helps ensure that doors close securely, which can enhance safety and energy efficiency by preventing drafts. Door closers are commonly used in commercial buildings, schools, and homes. These devices come in various types, including hydraulic, pneumatic, and spring-operated models. They can be adjusted to control the speed and force with which a door closes, making them suitable for different door sizes and weights. Proper installation and maintenance of a door closer can prolong its lifespan and functionality.