This is a rath, the Irish term for a ringfort, the most common type of early medieval settlement monument in Ireland. Typically dating from roughly the sixth to the tenth centuries, raths were enclosed farmsteads, the homes of farming families whose status was marked by the effort of raising a bank and digging a surrounding ditch. What makes Knockeenboy quietly compelling is not dramatic scale but the persistence of its detail: a near-circular enclosure measuring 33 metres north to south and 32 metres east to west, its earthen bank still standing a metre high in places, its external fosse, or ditch, still traceable around the eastern to south-south-western arc at around 0.6 metres deep.

The original entrance appears to survive as a gap roughly four metres wide in the bank to the north-east, which is a typical placement for ringfort entrances. Inside, a slight scarp running on an east to west axis crosses the interior, a subtle surface change that may hint at the position of former structures or yard divisions, though the pasture now covers whatever once stood there. What deepens the interest of this particular site is a souterrain recorded in the adjoining field to the south-east. A souterrain is an underground stone-lined passage or chamber, often associated with ringforts and used variously for storage, refuge, or both. The fact that it sits just outside the enclosure rather than beneath it is not unusual; souterrains were sometimes constructed in close proximity to a rath rather than directly within it, and the two features are almost certainly related, representing different parts of what was once a single farm complex.