A small shelter once stood near the south-east perimeter fence line, approximately 36 metres north-north-east of the railway line directly in front of the F1 gun. The structure has long since been demolished and no remains are visible today.

Very little is known about this building. Based on 1955 aerial imagery, it appears to have been no larger than around 3 square metres and may have been little more than a simple concrete box. Its small size suggests it served a limited, practical function, possibly as temporary cover or storage rather than as an occupied space.

Today, only scattered fragments of debris remain on site, marking the location of a structure that has otherwise disappeared.