I cut a small piece of stove pipe, about 3 inches. (HINT) To get a close measurement place the top barrel in the seperator legs and hold the collar up to the bottom barrel. This will let you get close to the size of stove pipe.
	Then I placed the small piece of stove pipe on the damper of the bottom barrel. I used it to hold the top adaptor in place while I marked the holes.
	As you see in this photo, I've used the scribe to mark the outside of the vent. I also marked two of the screw holes.
	I drilled out two holes and mounted the vent. Then marked and cut out the damper opening. Once again I put the top barrel back on the bottom to check fit the collar.
	Here is the final mounting of the vent damper. You will need to do this on the other end of the barrels as well. You can follow these instruction for the other lower vent damper.