FUNCTION: The door handles have a small rotary knob on one side for internal door locking and a safety release function on the other side. The door can be locked and unlocked from the inside with a simple turn of a knob. They are used for interior doors to combine security and privacy. DURABLE DESIGN: The sturdy construction of these door handles makes them strong, sturdy and durable. The sturdy handle design prevents rattling and breaking that can occur with inferior mortise door handles. The polished brass finish adds a touch of elegance to your home or office. SAFETY: These polished brass door knobs feature a safety feature on the exterior door knob. By using the supplied override key, the door can be unlocked quickly and safely from the outside in an emergency. These security buttons are not designed for use with normal lock and unlock keys. APPLICATION: These door locks can be used on interior doors with a thickness of 35mm to 45mm. The tubular latch is adjustable to 60mm or 70mm (the distance between the center of the hole and the edge of the door). They are suitable for both commercial and domestic applications.INSTALLATION: These chrome door handles come with fitting instructions and templates for easy installation. All fixtures and accessories are supplied with color matched screws, tubular latch and override key. This set of knobs can be used for left or right doors.