What makes it worth attention are two deliberate depressions worn into its upper surface, each roughly the size of a cupped hand. These are bullauns, bowl-shaped basins carved or ground into stone, found at early medieval and prehistoric sites across Ireland, often near churches, holy wells, or liminal places where land meets water. Their precise function remains genuinely uncertain; they have been associated with grinding, with ritual water collection, and with cursing stones, small rounded rocks sometimes rotated in the bowls as part of folk-religious practice that persisted well into the post-medieval period.

The Carrigeenduff boulder is earthfast, meaning it is fixed in the ground rather than a loose surface stone, and measures roughly 1.1 metres from north to south and 0.8 metres east to west. Its southern end rises about 0.3 metres above the ground surface, while the northern end sits level with it, giving the whole thing a slight tilt. The first bowl is cut into the flatter southern portion: steep-sided and nearly circular, with a diameter of around 0.27 to 0.28 metres and a depth of 0.16 metres. The second basin sits approximately 0.18 metres to the north of the first, similar in diameter but noticeably shallower at its northern edge, deepening toward the south. The pairing of two basins on a single boulder is not unheard of in Ireland, though it is far from the norm, and the proximity of the site to running water and boggy ground fits a pattern seen at many bullaun locations elsewhere in the country.