By the time cartographers recorded it on the Ordnance Survey six-inch map of 1842, the site was already being bisected by a road running northwest to southeast, cutting straight through what had once been a roughly circular earthwork enclosure of about forty metres in diameter. Today, no visible surface trace remains.

A rath, as ringforts of this type are commonly known, would originally have consisted of an earthen bank and ditch enclosing a domestic settlement, most likely dating from the early medieval period, roughly the fifth to twelfth centuries, when this form of enclosed farmstead was widespread across Ireland. Thousands were built, and many have since vanished beneath farmland, roads, and later construction. The Garryduff example sat on an east-facing slope, a practical choice that would have offered morning light, some shelter from westerly weather, and reasonably well-drained ground. That the 1842 map still showed it as a legible circular enclosure, even a damaged one, suggests it retained some earthwork presence well into the nineteenth century before disappearing entirely from the landscape.