They are easy to miss. The decorated surface measures roughly half a metre by a third of a metre, and the motifs cut into it are faint enough that low raking light is usually needed to read them at all. What survives includes an oval cupmark, a cup-and-ring motif, and scattered areas of pickmarks clustered around both. Cupmarks are shallow, roughly circular depressions ground or pecked into stone, and when a cupmark is surrounded by one or more concentric rings, the result is called a cup-and-ring motif. Both forms are found across Atlantic Europe and are generally associated with the prehistoric period, though their precise meaning remains genuinely unknown. Here, the cup-and-ring's outer ring is described as very faint, its depth only two or three millimetres, which gives a sense of how close to vanishing this carving has come over the millennia.

The boulder itself is oblong, about three metres long and just over a metre wide, with a flat upper surface that faces broadly south-east at around 150 metres above sea level, looking out over the valley of the Kealduff River. It sits within the remains of an old field system, which suggests the land has been worked and reworked across very different eras, prehistoric carvers and later farmers occupying the same slope without necessarily knowing much about one another. A second example of rock art lies approximately 80 metres to the west, which raises the possibility that this part of Knockaunanattin once held some significance that is now almost entirely lost to us, the carvings themselves the most durable remnant of whatever that significance was.