Excellent operability, the SL99 series is a hook lock with a malfunction prevention device

■  Magnet type trigger for malfunction prevention (PAT).
Since  the  magnet  type  trigger  is  mounted,  never  to  be locked while the door is opened.
■  Protector with the illegal unlocking prevention
When locking, the protector comes out along with the sickle deadbolt, and prevent illegal unlocking from gap of the door. 
Also, you cannot operate the sickle deadbolt by lifting the door.