Three stones on a hillside, arranged in a line that runs north to south, have been standing in the Comeragh Mountains long enough that nobody can say with any confidence why they were put there. Two remain upright; the third has been reduced over time to a low stump, barely breaking the surface. Taken together they span just under seven metres, a modest row by the standards of prehistoric stone alignments, yet their placement is deliberate and considered, set at the bottom of a south-west-facing slope, on the inner edge of a natural spur of high ground that pushes out to the south-west.

Stone rows, sometimes called stone alignments, are a feature of the Irish Bronze Age landscape, though their precise function remains a matter of debate among archaeologists. Some are thought to relate to astronomical observation or seasonal markers; others may have defined boundaries or ceremonial approaches. The three stones at Knockanaffrin are made from conglomerate, a sedimentary rock composed of rounded fragments cemented together, which gives each stone a rough, pitted surface. The southernmost stone is rectangular and crested, standing 1.72 metres high; the central stone is slightly taller at 1.78 metres, subrectangular in shape and coming to a point at the top. Between them the gap is relatively short, just 1.3 metres, while the northern stump sits 3.75 metres further along the line, that uneven spacing perhaps reflecting the original intention of the builders, or perhaps the result of a lost fourth stone somewhere in between. The asymmetry gives the row a slightly unresolved quality, as though part of the sentence has been swallowed by the mountain.