This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, typically consisting of a mound of fire-cracked stone built up beside a trough where water was heated by dropping in stones from a fire. The example at Knockskehy is a substantial one: roughly 18 metres east to west and nearly 15 metres north to south, standing about 1.2 metres high, with a wide opening of 5.6 metres facing west. The northern arm of the horseshoe extends further than the southern, and a small circular depression, about a metre across, sits just inside the opening on the western side, possibly the remnant of the trough itself.

What gives this particular site an added layer of interest is what turned up in the boggy ground immediately to the south-east in 1986. Two worked oak timbers were found there, clearly shaped by human hands. The larger piece, nearly 5.8 metres long and broken at both ends, had a channel cut along its length, roughly central, measuring about 12 centimetres wide and 5 centimetres deep. The smaller piece had a U-shaped end with bevelled inner edges. Timbers like these are associated with fulacht fia sites and are generally interpreted as components of a wooden trough or conduit used to hold or direct water during the cooking or heating process. The preservation of organic material such as wood is relatively rare in Irish archaeology, and finding pieces this size, retaining clear evidence of deliberate shaping and joinery, makes the Knockskehy discovery quietly significant among sites of this type.