Shoe-fitting fluoroscope. 6:26 video:
https://www.youtube.com/watch?v=_hAufRLMd0c
More: https://en.wikipedia.org/wiki/Shoe-fitting_fluoroscope
Previously:
https://www.homemadetools.net/forum/...579#post159016
https://www.homemadetools.net/forum/...741#post152100
https://www.homemadetools.net/forum/...152#post115730
https://www.homemadetools.net/forum/...561#post151493
https://www.homemadetools.net/forum/...004#post100479
https://www.homemadetools.net/forum/...186#post130478
https://www.homemadetools.net/forum/...228#post126506