What makes this particular rath, or earthen ringfort, worth a second look is how thoroughly the landscape has done half the work of enclosure. On the south, west, and north sides, a bank of earth and stone between four and five metres wide and still standing roughly seventy centimetres above the interior defines the perimeter in conventional fashion. But to the east, where the ridge falls steeply away on its own, there is no bank at all. Instead, the defining feature is a scarp, a cut or natural edge in the ground, that simply merges with the hillside below it. No fosse, the defensive ditch that typically accompanies such banks, has been identified anywhere around the circuit.

Ringforts of this kind were constructed across Ireland throughout the early medieval period, broadly between the fifth and twelfth centuries, and served as enclosed farmsteads for individual family groups. They are among the most common archaeological monument types in the Irish landscape, with tens of thousands recorded, yet each one carries its own peculiarities of construction and setting. The Barnabrack example, roughly twenty metres in diameter internally, is relatively modest in scale. Its builders appear to have read the ridge carefully, relying on the pronounced natural slope of the east face as a ready-made defensive element and concentrating their labour on the more exposed western arc. A modern field boundary now runs along the outer foot of the bank from the northwest through to the north-northeast, complicating the original outline at that section and making any trace of the original entrance impossible to identify.