This photo comes to you from the Arcadian, er, Centennial, no wait I mean Calumet and Hecla mill. The mill started life processing copper-bearing rock from the short-lived Arcadian mine, and was quickly bought up by the Centennial Mine -- which eventually fell into the hands of the great Calumet and Hecla, and that was that. This mill is hidden in the woods on the shores of Portage Lake, slowly succumbing to nature.
I have no idea what this bracket is, except that the mill floor is covered with them. The mill was extremely modern when it was first built -- the Arcadian mine was funded by John Rockefeller himself, and spared no expense. The ruins look much more modern than 1913 (the year they were actually built), but regardless -- they're still ruins.