Fireplace Damper Sign - Solid Brass by Upper Deck Brass STYLISH SAFETY. Show 'damper open' and 'damper closed' on each side. HOW IT WORKS. After closing or opening flue, flip sign to correct side. MADE FROM SOLID BRASS. Damper sign made from solid brass. EASILY READABLE SIZE. Measures 1.5 inches x 3.5 inches.