Thousands were built across the country, yet each one that survives into the present does so by its own particular accident of land use and luck, and this one at Knocknabinny persists as a low earthen platform rather than any dramatic earthwork.

The fort is roughly circular, measuring about 24.8 metres north to south and 25 metres east to west, with the raised area standing some 1.4 metres above the surrounding ground. A rath, as this type is known, would originally have consisted of a circular bank and ditch enclosing a domestic space, home to a farming family and their livestock. What makes this example quietly interesting is the cartographic record of its slow erosion. On the Ordnance Survey six-inch map of 1842, it appears as a hachured penannular enclosure, meaning the surveyors recorded it as an almost-complete ring with a gap, the hachures being the short radiating lines used to indicate an earthen bank or raised feature. By the 1902 revision, it had diminished further and was recorded only as a hachured semi-circle. Comparing the two maps gives a precise, if melancholy, picture of what a century of agricultural pressure can do to an earthwork that nobody is actively protecting.