So this is realllly hard to explain on paper. At least for me. So I drew some basic designs in MS Paint hahah. Here we goooo....
This would be for a closet grow most likely...
buy a cheap HOLLOW door.
take it apart.. so you have one part like |_______| and one like ------------- (bottom/top view)
now cut and glue a separator into the door.. so it looks like this. |_____|_____|
then, on the side facing the closet, cut two holes. on the RIGHT side of the door AS YOU ARE FACING IT, cut a hole at the BOTTOM. for the intake fan.
I seriously hope you understand that lol. If not ask me anything I know the drawings are POS's. Oh and its not marked with a 1.. but the top right circle on the grow box is where i was referring to.