This structure was completely below ground with raised entrances level to the surface and was aligned north-east to south-west. The north-east entrance was 42cm above the chamber roof and measured 5.55m long by 1m wide. The southwest entrance 56cm above the chamber roof and measured 6.15m long by 1m wide. Each entrance was capped by corrugated iron covered in concrete that sat on identical lips in the entrance wall, 5cm deep at the sides and 10cm deep at the entrance and chamber ends of the entrance. Both entrances were blocked by earth and rubble although access was just possible via the north-east entrance. It was not possible to ascertain the number of steps at either entrance but both led to a corridor, each of which contained an 87cm deep recess complete with centrally located exhaust vents and had poured concrete floors with five 60cm by 46cm concrete slabs set into them.
The central chamber was identical to shelters F1-F6 in terms of measurements and fittings. <1>