NOTICE! Your custom built fireplace door will be as accurate as the measurements provided on this sheet. Use a rigid tape or metal ruler for exact measurements. A mounting flange will protrude into your fireplace opening 2 to 3 inches and be sized to allow 1/4" space between it and your opening. Holes will be drilled though this flange into masonry for attachment. A high temperature silicon or refractory caulking can be used to fill any voids between the door frame and your fireplace.