Enhanced safety and control - Allows you to open the door slightly to observe or ventilate without compromising security. This helps you check visitors or let air in while keeping everyone protected. High-strength steel reinforced chain - The chain lock is reinforced with steel, offering high strength and durability. External tampering or prying requires significant force. Thickened, robust construction - Built with a thickened body and a sturdy metal chain. Designed to withstand strong external influences and provide lasting security and reliability. Premium finish and appearance - Produced with an ultrahigh-temperature matte spray process. The smooth, attractive surface resists oxidation and color fading, maintaining a clean look over time. Practical use scenarios - Residential entry doors: Open the door a crack to see who is outside or to ventilate, while keeping the door secure. - Offices or classrooms: Ventilate during meetings or busy periods without giving up controlled access. - Hotels or rental properties: Screen guests and allow air flow before fully opening the door. Suitable for standard door configurations that accommodate a chain lock.