The positioning is deliberate in that way that early fortified sites so often are, making use of natural topography rather than fighting against it. The enclosure itself is modest, measuring around 22 metres northeast to southwest and just under 20 metres in the opposite direction, its outline now softened into the ground as a spread of grass-covered stone. Where the original facing-stones of the wall occasionally break the surface, they hint at something more substantial beneath.

This is a ringfort, or the remains of one. Ringforts, the most numerous class of monument in the Irish countryside, were typically enclosed farmsteads built during the early medieval period, roughly between the fifth and twelfth centuries, and they survive in huge numbers across Ireland in varying states of preservation. The Commons example has an entrance gap of nearly four metres on its east-south-east side, a detail that aligns with common practice in ringfort construction, where entrances frequently face eastward. The wall, where it can be traced, appears to have been around one to one and a half metres wide. Archaeological testing carried out by Martin A. Timoney approximately 70 metres to the east of the monument produced no related material, leaving the chronology and history of the enclosure itself still largely open.