Located and marked the position for the "Ultimate Ventilators." Drilled a 1/4 inch hole to center the hole saws. The inside hole was cut with a 2 1/2 inch (64mm) hole saw. The saw was applied by hand to ensure that it only cut into the foam and not into the outer skin. Once the inner hole was cut, a 1 7/8 inch (48mm) hole saw was used to cut all the way through. A thin knife was used to cut the foam to open the inner hole to the outer skin. This pair of holes almost perfectly matched the outer ring and raised inner ring on the vent.
