Abstract: There is provided the combination of first and second plates adapted to sandwich between them a panel to which they are to be affixed. The first plate has at least one boss projecting from one face thereof, and threaded shaft spaced from the boss. The boss defines a lip spaced from the face, at least part of the lip being directed generally toward the threaded shaft. The second plate defines a first edge adapted to be received under the lip, and a second edge adapted to lie adjacent the threaded shaft. The combination further includes a threaded nut for engagement with the threaded shaft, the threaded nut having a conical shoulder adapted to bear against the second edge of the second plate in such a manner as (1) to urge the second edge toward the first plate, and (2) to retain the first edge under the lip.