A cashel is a stone-walled ringfort, typically enclosing a farmstead or settlement during the early medieval period, and this particular annexe hugs its outer wall closely enough that the cashel's own stonework forms the enclosure's south-western boundary.

The enclosure is irregular in plan, roughly polygonal, measuring approximately 21 metres west-north-west to east-south-east and 17.5 metres north-north-east to south-south-west. Its walls are modest, about a metre wide and half a metre high, built from stone and covered in sod, with rounded corners giving the whole structure a softened outline. What makes the arrangement particularly interesting is the treatment of the southern wall. Rather than running straight across, it was built to avoid blocking the cashel's entrance, which lies immediately to the south. That careful accommodation suggests the enclosure was not a later addition tacked on as an afterthought, but was most likely built and used at the same time as the cashel itself, by people who knew exactly where the entrance was and intended to keep it clear.