Image Number 3 for United States Patent #6151841.
An inexpensive, prefabricated portable tornado shelter is disclosed. The shelter is assembled from four equilateral triangular sides, a base frame, and a floor, to form a square pyramid-shaped enclosure with latched doors and PLEXIGLAS windows. The shelter allows constant air pressure equalization between its interior and exterior. The shelter is held firmly to the ground with four auger bolts.