Key of the Bricked Door

Long brass with no cuts at all on the bit, and a bow rubbed thin on one side.

The key opens the door that used to be there. Held flat against any wall, floor, or ceiling that has held a door, gate, hatch, or window at any time in the last five hundred years, it reopens that opening for ten minutes, through brick, plaster, backfill, or later stonework of any thickness. Nothing happens on a surface that never had an opening, and it will not cut a way through undisturbed rock. Each old opening answers the key once and once only, and is shut for good afterwards. The way closes on its own with anything still in the gap pushed clear.