The larger of the two is a roughly rectangular, single-roomed hut, no more than four metres by three on its outer face, dug into the slope so that the builders could use the excavated material to raise the eastern wall and southern end. The walls themselves are built from medium to large uncut stone slabs packed with earth, and although the interior still holds fallen stones, no trace of a roof survives. A probable entrance in the south-west corner is marked by further tumbled stone immediately outside it, suggesting the structure was abandoned rather than deliberately demolished.

This is most likely a booley hut, a temporary seasonal shelter used during the old Irish practice of transhumance, or booleying, in which communities moved their cattle to upland grazing pastures in summer and erected rough huts to live in while tending them. The hut at Barnastooka overlooks an early nineteenth-century farmstead some 150 metres to the south-east, and it is thought the booley may have been abandoned around the time that more permanent settlement was established below. About twelve metres to the east, at the bottom of the same slope, a second and far more modest feature survives: a circular earthen bank barely visible above ground level, roughly 1.6 metres across externally, with an east-facing opening marked by a single stone. This is interpreted as a storage clamp, possibly used for keeping butter or cheese cool while the herdsmen were up on the summer pasture. The association between the two features, one for sleeping, one for storing dairy produce, points to a self-contained seasonal camp that functioned as a working unit before being left behind entirely. The site was identified during pre-development survey work carried out by John Cronin and Associates ahead of wind farm construction in Barnastooka.