The enclosure in question sits in improved pasture on a south-south-east-facing slope at Friarsfield, and the field containing it was already recorded as 'Rathnasmoorlane Field' on the first edition Ordnance Survey six-inch map of 1840, meaning the local memory of what lay there was embedded in the landscape long before anyone thought to measure it formally.

A rath is an earthen ringfort, the kind of enclosed farmstead that was built and occupied across Ireland from roughly the early medieval period. Thousands survive in various states of preservation; this one is oval in plan, running about 34 metres on its north-east to south-west axis and around 30 metres across. What makes it structurally interesting is that it retains a double enclosure: an inner bank, a fosse (a surrounding ditch), and an outer bank beyond that. The inner bank still stands to a height of around 0.85 metres on the interior side in its better-preserved sections, while the fosse ranges between roughly half a metre and just under a metre in depth where it remains legible. The outer bank, lower and less substantial, is clearest along the east to south-east arc. Two gaps in the circuit, one at the north-north-west and one at the south-south-west, may mark original entrances, though the surviving widths of 1.75 metres and 2.5 metres respectively are narrow enough to leave that an open question. Vegetation is reclaiming much of the northern side, and the interior is ungrazed, given over to tussock grass and encroaching briars. An adjoining earthwork lies immediately to the north-west, which suggests this was not an isolated feature in the early medieval agricultural landscape but part of something more clustered.