A rath, as these earthwork enclosures are known, was typically a circular or oval farmstead of the early medieval period, its bank and ditch enclosing a homestead and offering a degree of protection and status to whoever lived within. At Ballynagaul, what remains is an arc of earthen bank running from the south-west around to the north, with a diameter of roughly fifty metres. The rest has been levelled, absorbed over centuries into the surrounding pasture on its east-south-east-facing slope.

What makes this particular fragment worth attention is a detail in the construction. The inner face of the surviving bank is terraced, and that terracing is stone-faced. This is not universal among raths, and it suggests a degree of effort and craft beyond a simple heaped-earth boundary. The bank still stands to about 1.2 metres where it survives. The enclosure was recorded on the 1842 Ordnance Survey six-inch map, where it appears as a hachured circular feature, meaning the cartographers of the time noted and marked it using the conventional symbol for an earthwork or raised enclosure. That mid-nineteenth-century record is now among the better pieces of evidence for what the full circuit once looked like, given how much has since disappeared at ground level.