Step 1: Cut the Holes
Diameter of the first 2 holes is slightly over 4" to accept the 4" dryer vent hose. (A jigsaw cuts the best, a drywall jab saw wants to get stuck. I used a utility knife. Scary!...but the cut was great.) The third hole is a half inch bigger (4 1/2" diameter) so I can use the scrap as a cover for the unused vent hole. I am using cans that just happen to be the right 4" size. The cans will be used later to stiffen up the ends of the dryer hose.