A cashel is a ringfort built from stone rather than earth and timber, the drystone equivalent of the more familiar earthen rath, and this one retains its perimeter wall to a height of around two metres in places, with a width of two and a half metres throughout. At thirty-two metres in diameter, it is a substantial enclosure, its two wall-faces built from large, undressed limestone blocks laid in irregular courses without mortar.

What makes Cahertinny particularly interesting is how much ambiguity survives alongside the stonework. A gap in the south-west of the perimeter wall may be the original entrance, suggested by a well-built face on its northern side. A second gap to the south-east looks more recent, a later interference rather than a designed threshold. Inside, the space has been divided into three unequal sections by internal drystone walls, and in the southern section the remains of three or four structures are still visible beneath heavy overgrowth. Whether those structures belong to the cashel's original occupation or were added at the same time as the partition walls remains unclear. Against the outer face of the wall to the north, north-east, and east, there are small ruined rectangular enclosures that appear to be later additions entirely, possibly old sheep pens reusing convenient ancient stonework as a ready-made windbreak. An old north-south roadway runs just to the east of the cashel, and further structures have been recorded in that same direction, suggesting this was once a more populated landscape than its present quietness implies.