This probably comes under the heading of "dumb questions"...but here goes anyway. We recently picked up our BH 3010RE and brought it home. We are about 300 miles from the dealer, so don't want to go back for simple question. We have an exhaust fan from the under cabinet microwave to the outside, however there is a flapper cover on the exterior side of the vent opening that seems to be secured in place and does not open to allow air out. The flapper seems to be hinged at the top and is under an exterior vent hood, but I cannot seem to free up the lower side of the flapper. Are there catches here that I am not aware of? Told you it was a dumb question.