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Small enclosures surrounded by a strong embankment on two or three sides but open from the front (and in some cases also from the rear to cater for jet efflux or to permit entry of aircraft) to admit and store aircraft. Blast pens are also designed for storing or parking missiles, specialist vehicles, etc. Also called a hardened shelter.
An area protected on three sides by sandbags, concrete, compacted earth, or other material. The aim is to provide blast protection to the aircraft, weapon system, or essential equipment inside and beyond the revetment. Also called a blast fence, open blast pen, or hardened shelter.