The site is a rath, the Irish term for a ringfort, which was a type of enclosed farmstead built predominantly between the fifth and tenth centuries. Typically circular or oval, these were the homes of farming families of moderate status, their interiors protected by an earthen bank and, often, an outer ditch. At Ballyglass, despite the encroachment of gorse, hawthorn, and converted forestry ground, the basic anatomy of the monument is still legible underfoot.

The enclosure is a slightly raised oval, measuring roughly 34 metres north to south and 25 metres east to west. Its defining feature is a scarp, an earthen edge formed by the bank itself, which survives to a height of around 0.6 metres on the south side and rises to about 1.3 metres on the north, where the ground drops away more sharply. Outside the scarp runs a fosse, the external ditch that originally reinforced the enclosure's defensive or boundary function, here surviving as a shallow depression nearly three metres wide. The original entrance is still detectable as a narrow break in the scarp on the south side, though overgrowth has largely concealed it. More clearly legible is a causeway, about four metres wide, crossing the fosse at the north-north-east, which would have provided a secondary or perhaps principal point of access. Within the interior, the north-east quadrant holds a low, roughly circular rise of eight to nine metres in diameter; its function is not certain, but subtle internal mounding of this kind is sometimes associated with structural remains or earlier phases of use. A later field fence cuts across the western scarp, a common enough occurrence where agricultural boundaries have been laid down with little regard for what lies beneath. The rath is not isolated: another example of the same monument type sits approximately 230 metres to the north-east, a reminder that these enclosures often cluster, reflecting the dispersed but interconnected settlement patterns of early medieval Ireland. The northward views from the site, across low-lying pasture and bog, give some sense of the wider landscape these communities inhabited.