[SargeW]

There is not always a label for where to drill for the vent. I do not have any such label either and called Keystone for advice. Their reply was to call the dealer. I did, and the dealer didn't have a clue.

I would proceed by laying out the 4" circle on the wall where you think the vent would work, then with a small drill bit start drilling around the circumference of the intended location for the vent. The idea is to locate an area where there is no wall stud. Being that most of the wall is a layer of luan on each side of a sandwich of Styrofoam, there is a good chance that you will miss a wall stud. If you do happen to hit a stud, then move a few inches in either direction to find a clear area.

I will be doing the same in a day or so to locate the vent for my washer/dryer combo unit. Keystone will provide NO HELP for most technical issues, so you are on your own.