- Stick your head in the fireplace.
- Shine a flashlight up the chimney.
- Have a helper move the lever.
- You should have no problem seeing the damper move
- When it's closed, you yell to your helper "It's closed!".
- Make sure helper stops moving the lever at that point.
You can then look at the lever position and make a label indicating the closed position.
- Make sure there is no fire burning when you're doing this, you're not Harry Potter.
- Eye protection is recommended as moving the damper will possibly dislodge crud that you don't want in your eyes.
- Consider a face shield, as you probably don't want to come out of the process looking like Bert