The one at Coolcashla in County Mayo is a quiet example of a type that appears in boggy ground, beside streams, and on low-lying pasture from Kerry to Donegal. The name, loosely translated as "wild deer cooking place," points to one of the leading theories about their purpose: that these were outdoor cooking sites where water was boiled by dropping fire-heated stones into a trough. The stones crack and shatter with repeated use, and over time the broken fragments accumulate into the distinctive horseshoe-shaped mound that survives in the landscape long after the wooden trough has rotted away.

Most fulachtaí fia date to the Bronze Age, roughly 1500 to 500 BC, though some have produced dates stretching into the early medieval period. The basic method is consistent across sites: a timber-lined pit was sunk near a water source, filled with water, and then brought to the boil using stones heated in a nearby hearth. Experiments have shown the method is surprisingly efficient, capable of boiling a large volume of water in under half an hour. Whether the Coolcashla example was used for cooking, brewing, bathing, or some combination of purposes that archaeologists continue to debate, the crescent of burnt and shattered stone it left behind has persisted in the ground for millennia. Beyond its location in the Coolcashla townland of County Mayo, the specific details of this particular monument remain unrecorded in any publicly available form at present.