The earthwork, roughly 60 metres along its northeast to southwest axis and 32 metres across, survives as a faint depression rather than any imposing bank or wall. What remains of the surrounding fosse, a defensive ditch dug to define and protect an enclosed area, is shallow now, around a quarter of a metre deep and about ten metres wide, tracing an arc from southwest through west to northeast. The straight eastern side has been absorbed into a field boundary, the kind of quiet recycling of ancient lines that happens all across Ireland.

What makes Killerk particularly interesting is the layering of occupation visible when you look across different kinds of evidence. The 1903 to 1904 edition of the Ordnance Survey six-inch map recorded a short surviving stretch of levelled bank, as well as a linear earthwork oriented roughly north to south to the south-southwest of the enclosure. Within the enclosure itself sat the site of Killerk Castle, suggesting that whatever function this enclosed space originally served, it remained significant enough to attract later medieval settlement. Aerial photographs have added another layer: crop marks, the subtle discolouration of growing vegetation that betrays buried features below the soil, trace a curvilinear continuation of the enclosure extending into the adjacent field to the east. A field boundary there follows the same curve, as if the hedge-layers of a later century were, perhaps unknowingly, following the ghost of a much earlier boundary still legible in the ground.