The machine screws are 1-3/4" long and are nutted to hold the hatch in place, then nutted again with fender washers to hold the insulation in place. The perimeter of the sheet insulation is wedged in place by fit and the reverse angle of the hull.

The machine screws are 1-3/4" long and are nutted to hold the hatch in place, then nutted again with fender washers to hold the insulation in place. The perimeter of the sheet insulation is wedged in place by fit and the reverse angle of the hull.