The horizontal or click mill was a distinctively simple technology, common across Ireland and Scotland in the medieval and early modern periods, in which a wooden wheel was laid flat beneath the millstone, driven directly by a jet of water channelled from a stream. It required no complex gearing, no millwright of particular sophistication, and could be built and maintained by a small community. That simplicity made it ubiquitous in rural Ireland for centuries, which is part of why so few people now give the surviving traces a second glance.

What makes the Erry site quietly compelling is the density of what surrounds the mill remains. Within a short distance lie a church and graveyard, a castle with a bawn, and settlement earthworks to the north-east and east. A bawn, for those unfamiliar with the term, is a walled enclosure attached to or surrounding a tower house or castle, used to protect livestock and provide a defensive perimeter. The co-location of mill, church, castle, and settlement earthworks in one small area suggests this was once a functioning local centre of some kind, a community organised around the resources of those two converging streams, now reduced to low humps in the ground and scattered stonework.