The Ordnance Survey mapped it in 1842 as sub-rectangular; by 1902 and again in 1935, surveyors recorded a D-shape, the flat side of the D running along the eastern edge. Whether the feature itself changed, or whether successive surveyors simply read the earthworks differently, is the kind of question that makes these sites interesting rather than settled.

The enclosure measures roughly 32 metres north to south and 27 metres east to west. Its earthen bank stands about 1.5 metres high, which is modest but enough to mark a clear boundary across the sloping ground. On the exterior, a fosse, essentially a shallow defensive or drainage ditch, runs from the east around to the south-south-west, cut to a depth of around 0.5 metres. A causeway roughly 1.3 metres wide interrupts the fosse to the south, providing what would have been a controlled point of entry. The interior tilts downhill from east to west, following the natural slope. Enclosures of this general type are found across Ireland and could have served a range of purposes, from livestock management to the enclosure of a settlement or farmstead, though without excavation the function at Rathcuppoge remains open.