A fulacht fia, the term for a type of prehistoric cooking or heating site found across Ireland, typically consists of a horseshoe-shaped mound of fire-cracked stones beside a trough and a water source. Heat the stones in a fire, drop them into a water-filled trough, and you can bring the water to a boil without a pot. The stones fracture in the process, and over time the discarded fragments accumulate into the low, charcoal-flecked mounds that survive in the landscape today.

The six sites at Rathpatrick are arranged in a roughly linear formation along the north-eastern bank of a small stream running north-west to south-east. The ground here was formerly very wet and marshy, the kind of consistently damp terrain that fulachta fiadh seem almost to seek out, since a reliable water source was essential to their function. This particular mound measures seventeen metres north-west to south-east and twelve metres north-east to south-west, rising to just under half a metre in height. It is composed of small fire-cracked stones in a charcoal-rich matrix, partially covered by ploughed-up turfy sod still carrying the remains of reeds from its long-submerged past. The trough appears to face south-west, oriented perhaps towards the stream. A closely related site lies just seven metres to the south-west, suggesting this stretch of bank saw repeated, possibly coordinated, use over time. That six examples cluster so tightly along a single watercourse is unusual and raises questions about the scale or duration of activity here that the ground alone cannot yet answer.