EXTERNAL LOCKING LOCK is placed as a first but also as a second (additional) lock on each sliding sheet. It has a thickness of 10.5 mm. It provides maximum mechanical safety because the saw is screwed with four screws that catch the iron paddle. It is recommended by all insurance companies, even the police, against burglary. It is very easy to install at any height and still serves to keep small children out of the balcony. The main advantage is that it looks from afar whether it is secured or not, so do not forget the unsecured balcony doors when we leave, or even when we are inside. Has passed “HURRICANE” TEST in U.S.A. with the greatest success and proved to be the strongest sliding lock since 2002. Available in colors: White, Black, Brown, Silver