Narrow Lock Frame Design：Keeps the chain in place when the doorstop isn't in use, door and frame damage from a hanging chain. Ensure observation and ventilation while keeping the door safe Ideal for front doors, apartment doors, hotel rooms, and even sliding glass patio doors, additional security for your home or office doors are within reach! All installation hardwares are included in the package,so you can mount it easily. Narrow lock frame keeps the chain in a fixed position when the doorstop is not in use, avoiding door/frame damage caused by hanging the chain Door chain lock allows you to identify visitors before fully opening the door, providing additional security and preventing intruders from easily entering your property.