This is a rath, the Irish term for a ringfort, the most common type of early medieval enclosure in the Irish countryside. Farmers built them from roughly the sixth to the twelfth century as defended homesteads, throwing up a bank of earth around a domestic settlement and digging a fosse, an encircling ditch, just outside it. Tens of thousands once existed across Ireland; a remarkable number survive, though they are easily missed by those who do not know what they are looking at.

The Knockaderry example was recorded and compiled by Denis Power, with notes uploaded in August 2011. The enclosure measures 38.5 metres in diameter, enclosed by an earthen bank that reads very differently depending on which side you stand on. The interior height of the bank reaches only 0.6 metres, giving the inside of the rath a shallow, almost bowl-like quality as the ground rises gently toward the edges. The exterior height, however, climbs to 2.5 metres, a more imposing face presented to anyone approaching from outside. The external fosse varies considerably around the circuit: widest on the western side at 5.4 metres across and 1.65 metres deep toward the south and east, it shallows out noticeably as it runs from the north-west toward the east. The bank is at its most legible where it has been absorbed into the existing field boundary system running from south to north-west, though there is a gap of roughly six metres where it dips at the east-north-east, either through original design or later disturbance.

The site sits in working farmland, and a farm passage runs around the outer edge of the fosse from the south to the north-west, which incidentally offers one of the clearer ways to read the earthwork's profile without crossing the interior pasture. Because it occupies a north-facing slope, the interior can stay damp and the bank shadows fall long in the morning, which makes the subtle topography easier to read in low light. There are no formal visitor facilities, and the site is on private agricultural land, so any approach should be made with appropriate consideration for the working farm around it. The variation in the fosse, wide and well-defined to the west and almost imperceptible to the east, is the quiet detail that rewards a slow circuit of the outer edge.