The local name, recorded faithfully on Ordnance Survey maps, attributes the stone to Saint Patrick, crediting him with leaving behind both a chair and a knee print in the rock. The saint's association with nearby Croagh Patrick runs deep in this landscape, and such folklore routinely absorbed older sacred sites into the Christian tradition. But the real age of this stone's significance almost certainly stretches much further back.

Spread across roughly four square metres of the boulder's surface, on faces at various heights and angles, are more than 250 carved motifs, making it one of the most concentrated collections of prehistoric rock art in Ireland. Petroglyphs, meaning designs cut or pecked directly into stone, appear here in forms typical of the Irish Neolithic and Bronze Age tradition: cup marks, which are simple circular hollows; cup and ring marks, where one or more concentric rings surround a central cup; and less common keyhole designs. A further panel was uncovered as recently as 2015, suggesting the stone still holds surprises. Work by Bracken and Wayman in 1992 and by van Hoek in 1993 developed what became known as the rolling sun thesis: on approximately 18th April and 24th August each year, the setting sun appears to descend or glide along the northern slope of Croagh Patrick when viewed from the stone, as though the mountain itself becomes a kind of sundial. Whether those two dates held ritual significance for the people who carved the rock, or whether the alignment was deliberately chosen, remains a matter of careful study rather than settled fact.

The stone sits in open countryside south-east of Westport, and the proximity to Croagh Patrick means that on the two astronomically notable dates, the effect described in the rolling sun thesis can be observed in the evening from the site, weather permitting. The carvings are distributed across multiple surfaces at different levels, so it is worth taking time to move around the boulder rather than viewing it from a single angle.