Just got the parts today. I haven't got it together yet. Got the parts at Home Depot. 1...... 4" adjustable elbow 1.......4" plastic flapper for a dryer vent 1.......hose clamp 4 .......turn buckles I plan on sticking the flapper inside the elbow and securing with the hose clamp. Then I'll be hooking the hooks of the turn buckles in each corner of the square flange on the flapper. I will then use a piece of wire to to put in the eyes on the other end of each turnbuckle.The wire will go around the blower and hooked to the eye of the turn buckle on the opposite corner. Might use a coat hanger for this. I will turn the barrel nut to snug things up and seal around the blower opening with silicone. The reason I got an adjustable elbow is so I can angle the flapper down to adjust it to close better. If it doesn't work out, I can remove it easily and I'm only out $20. This thing is cheap, easy to do, and requires no electric to operate it. I just hope it works when its done. LOL! It is raining right now and I haven't got it hooked up yet. I haven't even fired up the furnace yet either, to see how well it works or doesn't work. Hunting season starts tomorrow so it may be a while till its done. What do you think? Will it work?