Also called a fulling mill, it was where woven woollen cloth was pounded and cleaned in water, a process that thickened and finished the fabric before it could be sold or worn. That such a mill once operated at Killagh in County Westmeath is known almost entirely because of a single line written down during one of the most methodical land surveys ever carried out in Ireland.

The Down Survey, conducted in the 1650s under William Petty as part of the Cromwellian settlement, mapped confiscated Irish lands in considerable detail. The terrier accompanying the Killagh parish map recorded the contents of the townland with blunt economy: a corn mill, a tuck mill, a ruined church, and a castle in repair. That castle is shown on the map standing on lands belonging to George Nugent, listed in 1641 as an Irish papist, a legal designation used at the time to identify Catholics whose property was subject to forfeiture. The castle itself was noted as still standing, which makes the ruined church beside it the older casualty, and the two mills nearby the working remnants of whatever local economy had survived into the mid-seventeenth century. Whether the tuck mill shown on the first edition Ordnance Survey six-inch map of 1838 occupies the same ground as the one recorded in the Down Survey is uncertain, but the possibility is a reasonable one, given how often mills were rebuilt on existing watercourses rather than moved.