I added a couple of vents to the back of the cabinet - one at the top and one at the bottom. I also needed to be able to control the size of the opening. Here is what I came up with...
I drilled two large holes.
Then I took some of my scrap wood and made these half-moon shapes.
Scrounged up a couple of bolts and drilled some holes.
And drilled some more holes.
And then put it together.
I tightened the nuts just enough to make it somewhat difficult to turn the cover. Now I can control the amount of smoke in the smoker.