OK... how does it happen..
buy the 2" or 1 1/2 " foam @ home depot or Lowes...
lay out lines with a fine point sharpie..
and cut it with a japanese pull saw.. or any cross cut saw will do..
I coat the edges where they will join with the PL polyurethane construction adheasive... [HD & Lowes ]
then I run 4" exterior screws to hold them together.. now these screws won't hold the foam real well .. used alone.... but when they go through the adheasive inbetween.. it coats the screws wth adheasive.. and it's taken into the second foam board... when it sets up in there.. it's the adheasive that holds it in there... not so much the threadding on the screws..
it's pretty easy
