A peephole is a small opening in a door or wall that allows a person to see outside without fully opening the door. Typically made of glass or plastic, peepholes are often used in residential and commercial buildings for security purposes. They provide a way to identify visitors before granting them access. Peepholes can vary in design, with some featuring wide-angle lenses to offer a broader view. They are commonly found in front doors and apartment entrances, enhancing safety by allowing occupants to see who is outside while maintaining privacy.