The door holder is a fail-safe unit energized by a power supply installed on large-scale building, between fire escape doors. It releases the armature plate allowing the door closer to close the door when the fire prevention system detects a fire alarm or emergency. The " PUSH OFF" button on magnet for instant release, the door can be opened or closed manually at any time. Also available in wall flush mount installation and optional stainless steel box for surface mount model.