The trench is all that visibly remains of a souterrain, an underground stone-lined passage or chamber built during the early medieval period, typically associated with nearby settlement enclosures and used for storage, refuge, or both. The flat stones are likely roofing slabs, displaced over the centuries as the structure above collapsed inward, leaving the depression that marks the feature today.

The souterrain sits within Knoppoge Fort, a ringfort, which is to say a roughly circular enclosure defined by earthen banks and ditches, the standard unit of rural settlement in Ireland from roughly the fifth to the twelfth century. Souterrains were frequently constructed inside or adjacent to these enclosures, their entrances sometimes concealed within the interior of the fort itself. At Dromidiclogh the relationship between the two features is still legible in the landscape, even if both have suffered considerably from time and agricultural activity. The scattered roofing slabs suggest the souterrain's stone-built roof was never buried deeply enough to survive intact once the surrounding ground shifted or was disturbed.