The one at Shinnagh in County Mayo is a quiet example of a type that appears in almost every county, yet rarely earns more than a glance from a passing walker. A fulacht fia typically survives as a horseshoe-shaped mound of burnt and shattered stone, usually positioned close to a water source. The mound is the accumulated debris of repeated use, the cracked and fire-reddened stones discarded after each heating cycle.

The accepted interpretation, supported by experimental archaeology carried out over recent decades, is that these sites functioned as outdoor cooking places. Stones were heated in a fire and then dropped into a water-filled trough, usually timber-lined and sunk into the ground, bringing the water rapidly to a boil. Meat could then be cooked in the trough, wrapped in straw or sacking. Most fulachtaí fia date to the Bronze Age, roughly between 1500 and 500 BC, though some have produced dates extending into the early medieval period. Alternative theories have proposed uses ranging from textile dyeing to bathing, and it is quite possible that the function varied from site to site and period to period. The Shinnagh example sits within a Mayo landscape that contains numerous such monuments, testament to how densely this part of Connacht was used and managed in prehistory.