Siemens SDH-8A Door HolderThe Siemens Model SDH 8 Series fire door holder is for use with overhead rolling doors, dampers, heat and smoke vents, self closing windows, as well as other special applications. Each unit consists of an electromagnet holding unit and angle bracket; a 'U' shaped bracket, and a latch arm. The holding unit, which has a light gray, hammer enamel finish, is equipped with a test switch. Mounting brackets are heavy gauge, cadmium plated steel. Moreover,