Replacing all the fire brick in our Wood Stove. It came with a Ash Tray that had about 9 holes drilled into the firebrick and the metal under them to allow the ash to drop. I have found most times the holes get plugged and we just empty from the fire box. I have 2 knobs to allow air into the box. Are the holes needed in the firebrick for fresh air or just to allow the ash to fall down. I figure it's not need for air as when I get a good layer of ash the holes are all plugged up anyway. Thanks for any answers.