The hill, known as Knocknamonaster, measuring roughly 160 metres east to west and 140 metres north to south, was not simply enclosed by the monastery; it was actively shaped and defended. Its slopes were scarped near the base to create a level platform on three sides, with a surrounding ditch and a counterscarp bank, the outer face of the ditch, rising between one and two metres high. A stone causeway once crossed the moat on the north side, connecting the knoll to the wider precinct, and by the time the Ordnance Survey mapped the area in 1837 this crossing was already recorded as a bridge in ruins.

Fore Abbey itself is a Benedictine house with origins in the medieval period, and Knocknamonaster formed a recognised part of its defensive precinct. The western gap in the counterscarp bank suggests a second gateway may once have stood there, and the system of defences likely extended eastward to meet a thirteenth-century gate on the south-east side, though that section has since been ploughed away and is no longer visible. On top of the knoll there are irregular earthen banks whose purpose remains genuinely unclear, resisting interpretation as any known building type or enclosure. Adding another layer of interest, a medieval dovecote, a structure used to house pigeons kept for meat and eggs, survives in the southern part of the hill. Dovecotes were a marker of some institutional or lordly status in medieval Ireland, and their presence on monastic sites is not unusual, though they are rarely so well contextualised within surviving earthwork defences as this one appears to be.