Parking space for aircraft, separated by blast walls
A revetment, in military aviation, is a parking area for one or more aircraft that is surrounded by blast walls on three sides. These walls are as much about protecting neighbouring aircraft as it is to protect the aircraft within the revetment; if a combat aircraft loaded with fuel and munitions was to ignite, a chain reaction might lead to the destruction of its neighbours. The blast walls around a revetment are designed to channel any blast and damage upwards and outwards, away from neighbouring aircraft.
Blast pen
A blast pen was a specially constructed E-shaped double bay at British Royal Air Force (RAF) Second World Warfighter stations, being either 150 ft (46 m) or 190 ft (58 m) wide and 80 ft (24 m) front-to-back, accommodating aircraft for safe-keeping against bomb blasts and shrapnel during air-attacks.
Although the pens were open to the sky, the projecting sidewalls preserved the aircraft from all lateral damage, with 12 in (300 mm) thick, 9 ft (2.7 m)-high concrete centres and banked-up earth on either side, forming a roughly triangular section 18 ft (5.5 m) wide at their base. The longer spine section behind the parking areas usually encloses a narrow corridor for aircrew and servicing personnel to employ as an air raid shelter.