STEP 1:
Drill 7/8″ or 1″ hole in duct at any angle. It can even be installed on an elbow! Insert damper rod through hole in duct.

STEP 2:
Hold damper firmly inside of duct and push down while tightening nut onto threaded rod.

STEP 3:
Align damper handle parallel with damper then push on handle to snap into place. Handle will now indicate open or closed position. Leave wide open.