FDC showing a cross section of proper bunker construction. Vertical timbers supported horizontal beams and PSP running at 90 degrees to the beams, that support first, a layer of dirt filled 105mm boxes, then 3 or 4 layers of sandbags. The bunker is partly underground, with empty ammo boxes filling the space from the ground to the PSP on the sides. Dirt taken from the hole is used to fill the bags and boxes but the bags are unfortunately the new model, made from plastic, that stacked poorly.

PSP was a hollow metal sandwich that was very strong and light, in a relative sort of way. It interlocked and we were told it could form a “portable runway” in locations with no fixed airstrip. That runway would have taken thousands of these sandwiches to land a cargo plane of any consequence.