It is a mullion, the type of vertical stone member used to divide the lights of a window, and it came originally from Leggetsrath in County Kilkenny. What makes it quietly arresting is precisely how little of it remains: a fragment roughly twenty centimetres long, just over ten centimetres wide, and fourteen centimetres tall, yet carefully worked and preserved rather than discarded.

The piece is held in the Office of Public Works store in Kilkenny, where it carries the depot reference KD017. It is cut from limestone and finished with chamfers, the angled transitional surfaces that soften the junction between a flat face and an edge, a technique common in medieval and early modern Irish stonework. The flat sides measure approximately seven millimetres across and the chamfers slightly more, at 7.5 millimetres, suggesting a window of modest but considered proportions. Notably, there are no glazing-bar holes, which would have been cut into the stone to receive the lead or iron armatures holding panes of glass in place. Whether this reflects the original design, an earlier date of manufacture, or simply the portion of the mullion that survives is difficult to say from the fragment alone.

Leggetsrath itself is a townland in County Kilkenny, and whatever structure this mullion once graced has left no obvious trace above ground. The stone now exists as an object lesson in how much architectural history is preserved not in situ but in depot shelves and conservation stores, removed from context but retained against the possibility of future understanding.