Partly because it is positioned on the south-eastern quoinstone, the dressed corner-block of the castle wall, and partly because a dense growth of ivy has long obscured its surface, the carving is barely discernible to the naked eye. What it depicts, however, is unmistakeable to anyone who knows the type: a sheela-na-gig, the enigmatic stone-carved female figures found on medieval churches and castles across Ireland and Britain, typically shown in an exaggerated, frontal posture with the genitalia prominently displayed. Their purpose remains genuinely contested; theories range from apotropaic warning figures intended to ward off evil, to fertility symbols, to survivals of pre-Christian belief embedded into Christian architecture.

The Ballyfinboy figure was described in detail by the scholar Barbara Freitag in her 2004 study of sheela-na-gigs. Her account draws out the carving's particular character: a neckless, earless female standing within a frame, her round head disproportionately small against thick, outward-turning arms. The ribs are clearly incised but there are no breasts. The arms reach from behind her splayed legs to clutch what Freitag identifies as the vulva, below which a further downward-pointing cavity is gripped by both hands. The knees and feet are turned outwards. It is, in other words, a figure carved with considerable intentionality, its anatomical strangeness the result of deliberate formal choices rather than crude workmanship. The castle to which it belongs, Ballyfinboy, is a tower house of the kind built widely across Munster and Connacht from the fifteenth century onwards, and the placement of such a figure on an exterior corner at first-floor level follows a pattern seen at other Irish castles where sheelas appear to mark thresholds or structural junctions.