A fulacht fia is, at its simplest, a prehistoric cooking site: a trough dug into the ground near a water source, filled with water, and heated by dropping fire-cracked stones into it. The broken, heat-blackened stones were then piled to the side, and it is these distinctive mounds of burnt material that survive as the most visible evidence of the practice. The site at Knawhill sits on the southern bank of a stream, which would have supplied the water essential to the whole operation.

The mound here was apparently levelled around 1978, according to local memory, which means what remains is a low, spread deposit rather than the more recognisable horseshoe-shaped earthwork that survives elsewhere. The site is likely one of three fulachta fiadh identified in the same townland, a clustering noted by Bowman as far back as 1934. That density is not unusual; fulachta fiadh are among the most commonly recorded prehistoric monument types in Ireland, and they tend to appear in groups near watercourses, which makes the Knawhill concentration consistent with a wider pattern of repeated use of particular landscapes over long periods of time.