I need to install a 4" dryer vent thru my floor of my laundry room.The reason for going thru thr floor is because the room is in the middle of the house and there's no exterior wall in the room. It will go into the crawl space and out through the closes wall.My question is after I cut my 4 1/8" hole through the floor, what do I put through the hole and how is it attached? I can't seem to find any duct piece made for this.