The mound measures roughly 14.4 metres by 15 metres and rises just 1.1 metres at its highest point, dipping lower on its south-western side and hollowed at the centre. A stream curves around its northern and eastern edges, and that proximity to running water is no accident. This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, typically Bronze Age in date. The usual interpretation is that stones were heated in a fire, then dropped into a water-filled trough to bring it rapidly to the boil. Over repeated use, the cracked and spent stones were raked out and piled up, and it is precisely that accumulated debris, darkened and fragmented, that forms the characteristic horseshoe-shaped mound visible today.

What makes Knockduff quietly noteworthy is that it does not stand alone. A second fulacht fia lies approximately 80 metres to the south, which hints at repeated, perhaps sustained activity in this particular spot over time. Whether both sites were in use simultaneously or represent episodes of return across generations, the clustering suggests this stretch of ground beside its stream was a known and valued place. The burnt mound at Knockduff is typical in form but the pairing with its near neighbour gives it a slightly different quality, less an isolated curiosity than a fragment of a wider pattern of prehistoric land use in the Cork countryside.