The High Sliding Door Child Lock is a child proofing lock that prevents children from opening patio doors and escaping to the patio or balcony. It installs at the top on the side edge of most patio doors and prevents the sliding door from opening more than 4 inches. This provides ventilation but stops the child. It can be operated from either side of the door and can be mounted on the left or right side. It also disengages for periods of non-use. Green/Red locking indicator. Minimalistic design blends in.