Vascular stent.
https://diqn32j8nouaz.cloudfront.net...t_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...702#post151948
https://www.homemadetools.net/forum/...035#post157123
https://www.homemadetools.net/forum/...210#post188264
https://www.homemadetools.net/forum/...686#post186282
https://www.homemadetools.net/forum/...706#post178581