During World War II, what were "Anderson shelters", which were usually put in back gardens, made of?

Question

The initiative for what current unit of the British Army was begun during World War II in 1941 by David Stirling as a commando force operating behind enemy lines during the war in North Africa and Europe?

Answer 1

Corrugated iron
Installed in a pit and covered with earth, they were "do it yourself" bomb shelters, most frequently used in London during the blitz. 6 ft (1.8 m) high, 4 ft 6 in (1.4 m) wide, and 6 ft 6 in (2 m) long, buried 4 ft (1.2 m) deep and covered with a minimum of 15 in (0.4 m) of soil above the roof, they could hold 6 people.