From verso of card: "This picture shows a type of dug-out suitable for construction in a garden. It is gas-proof, and will give protection from blast and splinters from high explosive bombs. The excavation is in the form of a trench 7 ft. deep and 6 ft. wide at the top and 4 ft. wide at the bottom. The earth sides are supported by corrugated iron sheets held in place by uprights. . . . The roof consists of corrugated iron sheets resting on wooden joists laid across the excavation. Inside the entrance is an air lock formed by 2 gas curtains. Outside the dug-out, steps lead down from one side to the entrance."