Why black is not recorded, though the name suggests something once distinguished this enclosure from its neighbours, perhaps the colour of its soil, the darkness of its vegetation, or some older association now lost entirely.

The structure itself is a univallate rath, meaning it is defended by a single enclosing bank rather than the two or three concentric rings found at more elaborate sites. A rath is an earthen ringfort, the most common monument type in the Irish landscape, built primarily during the early medieval period as a farmstead enclosure for a family of some local standing. At Lackaboy, the bank is substantial: 7 metres wide at its base, rising to a maximum external height of 2.8 metres, with the interior sitting roughly 1.8 metres below the top of the bank. Outside the bank runs a fosse, a defensive ditch, here measuring 2.2 metres wide and 0.8 metres below the level of the surrounding land. The entrance, which faces south, is a generous 6.4 metres across, wide enough to have admitted livestock with ease. The interior measures approximately 37 metres north to south and 39 metres east to west, giving a usable enclosed area that would have accommodated a household, outbuildings, and animals. The interior floor sits slightly above the surrounding pasture and slopes gently southward, a detail that would have aided drainage. These proportions and features, recorded in the North Kerry Archaeological Survey published in 1995 by C. Toal, place Lisduff firmly within the well-understood tradition of early medieval enclosed settlement, ordinary in type but well preserved in its dimensions.