This structure was completely below ground with raised entrances level with the surface. The shelter was aligned north-east to south-west. The north-east entrance was 42cm above the chamber roof and measured 6.55m long by 1m wide. It was capped by corrugated iron covered in concrete, which sat on a lip in the entrance wall, 5cm deep at the sides and 10cm deep at the entrance and chamber ends. Twelve steps led down into a corridor (70cm wide) ending in a recess (87cm deep). The south-west entrance was 38cm above the chamber roof and measured 6.25m long by 1m wide, capped with concrete-covered corrugated iron sitting on an identical-sized lip in the entrance wall. Eleven steps led down into a corridor identical to that of the north-east. Both recesses had a 10cm-diameter exhaust vent centrally located in the roof, and each had a poured concrete floor with five 60cm by 46cm
concrete slabs set into it.
The central chamber externally measured 7.4m by 1.85m by 2.45m high with an internal measurement of 1.54m at its widest point. The chamber was of unpainted concrete and had the same benches as shelter F1. Evidence of shuttering is clear and the construction technique is identical to that of shelter F1. Sixteen 60cm by 46cm rectangular slabs extended down the centre of the chamber and three more exhaust vents were located at equal distances within the roof.
Both the recess and the internal doorways had the remains of iron hinges and the internal door had the remains of an iron latch, indicating that doors were at one time present. Iron hook latches were affixed to the external wall of the entrance approximately 1m off the floor. <1>