Most early medieval Irish fortifications are roughly circular, following the familiar rath or ringfort tradition. A deliberately rectangular enclosure defined by multiple banks and fosses, a fosse being a defensive ditch dug to reinforce an earthen rampart, points instead towards a later, possibly post-medieval military function, though the precise origin of the site remains unclear.

The antiquarian T. J. Westropp, writing in 1909, recorded a more elaborate arrangement on the northern side: three banks and two fosses, giving the fort a layered, almost formal defensive profile. That complexity has largely been lost. By the time of more recent survey work, the northern side had been so thoroughly levelled that only two very low, broad banks and a shallow fosse remained legible. The southern and western sides preserve the earthworks more clearly, with the outer western bank still standing to an external height of over a metre. The enclosed rectangular area is substantial, roughly 78 metres north to south and 65 metres east to west, large enough to have sheltered a meaningful body of men and equipment. The eastern side has been further damaged by a long bohareen, a narrow rural lane, which cuts through that flank of the enclosure.

The name alone raises questions that the landscape cannot fully answer. 'Garrison' implies a body of soldiers stationed at a particular place, but who garrisoned it, and when, is not recorded. The fact that the name was already fixed on the 1842 map suggests it had been in local use for some time before that, carrying the memory of a military presence that the earthworks themselves can only partly corroborate.