What looks like an ordinary grassy mound turns out to be a carefully engineered enclosure some 26 metres across, its outer bank still standing up to 1.6 metres high on the exterior face. Most striking is the construction of that bank: large rubble boulders have been roughly laid against its outer edge to form a revetment wall between one and 1.2 metres tall, best preserved along the south-western to north-western arc. This kind of stone-facing was a way of reinforcing an earthen bank against slippage and erosion, and its survival here, even partially, gives some sense of how substantial these enclosures once appeared in the landscape.

Raths, the ringforts of early medieval Ireland, were typically the enclosed farmsteads of prosperous families, built roughly between the fifth and twelfth centuries. The Killeenduff example follows the classic pattern in broad terms, with a single entrance break, about 3 metres wide, opening at the north-north-west. But a few details complicate the tidy picture. There is no trace of a fosse, the defensive ditch that commonly runs outside a rath's bank, at ground level. The interior itself is not flat: the north-western quadrant sits noticeably higher than the rest, defined by a scarped edge on its southern and eastern sides. That internal platform, roughly 11 metres by 13 metres, may once have supported a structure. The site also contains a souterrain, an underground passage or chamber built from stone, which are typically associated with storage, refuge, or both. Their presence in a rath generally suggests the enclosure was in active use, not merely a symbolic boundary. An old field bank running roughly east to west has also merged with the outer face of the rath on its northern side, folding the prehistoric monument into a later pattern of land division.