a slate floor tile that takes and retains the footprint of the last person recorded as absent.

Square tile of dressed slate with a matte surface. When laid level upon a rigid substrate, the tile develops a shallow impression of a shoe sole. The impression appears without applied load and forms within 3–9 minutes after a spoken denial of presence is made in the same room. The denial must be made by a person who was physically present at the time in question, as later established by independent means. If multiple denials are made, only the last qualifying denial is retained.

The impression matches the outsole pattern, size, and wear of the denier’s footwear at the time of denial, including defects. If the denier is barefoot, the plantar ridges are reproduced with partial clarity. Washing, abrasion, and re-polishing do not remove the impression. Cutting the tile destroys the phenomenon and yields inert slate. The tile has been used to verify staff attendance records; one dismissal followed.