National door secure guard provides an increased security for wood or metal doors. The guard allows you to open the door slightly for ventilation or viewing while resisting an unwanted entry. It's a great brand for securing your homes, offices, other spaces. Absolutely durable, the products from National provide excellent quality. They have always tried to produce good quality, safety-identification products to help make the world safer place to be in. They try to deliver the highest quality products in the fastest way possible. Providing a safe environment by making the best quality products is their only motto.1) Secure lock cannot be unlocked from the outside 2) Unlocks easily from the inside without a hassle 3) Die castZinc with bright brass finish 4) Ideal for limiting door openings in residences