The structure, estimated at roughly 38 metres in diameter, has been levelled entirely, leaving no visible surface traces in the grass. The name alone survives, which in its own way tells you something about how long local memory can outlast the physical evidence of a place.

What the site probably represents is a ringfort, the most common type of early medieval enclosure found across Ireland. Ringforts, typically circular earthen banks enclosing a domestic or agricultural space, were built and used roughly between the fifth and twelfth centuries, and tens of thousands of examples once existed across the island. Many have been destroyed by ploughing, drainage, and land improvement over the centuries, leaving only a name on a map or a slight irregularity in a field. The "Gallows" element of this particular name is harder to explain with certainty, though such placenames in Ireland sometimes reflect a later medieval or early modern association with a site of execution or judicial authority, grafted onto an older structure whose original purpose had long since been forgotten. Whether that association was literal or merely traditional at Knocknacroagha is now impossible to say.