The ringfort at Knockagarry is a near-perfect circle, measuring 43 metres east to west and 42 metres north to south, its circumference traced by an earthen bank and an outer fosse, the fosse being a defensive ditch dug just outside the bank. Neither feature is especially dramatic at this point; the bank rises only about 0.65 metres on its interior face, and the fosse reaches a depth of around 0.7 metres at its deepest. But understatement is rather the point with these structures. They were built not to impress from a distance but to mark out a farmstead, to signal ownership, and to keep livestock in and wolves, or neighbours, out.

Ringforts, sometimes called raths when they are earthen rather than stone-built, are among the most common archaeological monument types in Ireland, with tens of thousands surviving across the country. Most belong to the early medieval period, roughly the fifth to twelfth centuries, when they served as the enclosed homesteads of farming families across the social spectrum. The example at Knockagarry sits on a south-facing slope, which would have been a deliberate choice, offering shelter from northerly winds and maximum exposure to low winter sun. The interior slopes gently downward to the south and is now grass-covered. There is a substantial break in the bank to the north-north-west, about seven metres wide, which is likely the original entrance, along with further gaps to the south-south-east and south. Multiple openings are not unusual in raths of this type, though some gaps may have developed through later agricultural use of the land rather than original design.