Mine is 2 sheets of insulation. My DSIL built a frame out of 2x2's to support the insulation and hold the 2 sheets together. He then screwed through the 2x2's into the studs in the wall (there are 4 screws). It has been up 10 years -- he thought he would have to replace the insulation but it has held up real well (even though I frequently put pins in it).