Enhanced security and privacy - The door chain lock adds extra protection to prevent others from sneaking into the room, and it allows you to keep the door slightly open for observation and ventilation. Child and pet safety - Can be installed out of reach of children to prevent them from opening the door, providing additional protection. It also helps prevent pets from opening the door or leaving a gap for pets to pass through. Wide compatibility - Classic chain lock suitable for many door types and locations, including home front doors, bedroom doors, apartments, rental rooms, dormitories, hotel doors, basement doors, storage room doors, cabinet doors, windows, and more. Durable construction - Made of high quality stainless steel, rustproof and wear-resistant. The plate and chain are thickened to provide greater strength and stability. Edges are polished for a smoother finish. Longer and thicker stainless steel screws enhance security. Use scenarios - Hotel or dormitory interior doors: maintain privacy while allowing ventilation. - Homes with children or pets: restrict door opening to prevent accidental exits or escapes. - Rental or shared living spaces: enhance security by limiting door access while still allowing observation.