The earthwork at Lackan sits on a slight natural rise in gently undulating grassland, and what remains is a sub-circular enclosure roughly 35 to 36 metres across, its perimeter earthen bank worn down to little more than a scarp in places, broken by several disturbance gaps, and interrupted by modern field fences at the south-west and north-west. A laneway running roughly north to south cuts through the western side, a detail already visible on the Ordnance Survey six-inch map of 1837, suggesting the road has been slicing through the monument for at least that long.

Ringforts, sometimes called raths, were the most common form of enclosed rural settlement in early medieval Ireland, typically built between roughly the fifth and twelfth centuries. They served as farmsteads, their earthen or stone banks defining a space for a household and its livestock. The Lackan example was recorded on the 1837 OS Fair Plan map as an oval enclosure drawn with two concentric lines and labelled simply as "fort", which reflects a long tradition of marking such features on Irish maps even when their origins were poorly understood. Inside the enclosure today, faint traces of cultivation ridges run north to south, evidence of later agricultural use that has further softened whatever original form the interior once held. A second ringfort lies approximately 200 metres to the north-east, a reminder that these monuments frequently occur in clusters, reflecting the density of early medieval farming communities across the Irish midlands.