Pneumatic reciprocating saw.
https://diqn32j8nouaz.cloudfront.net...w_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...392#post150810
https://www.homemadetools.net/forum/...335#post185164
https://www.homemadetools.net/forum/...005#post157032
https://www.homemadetools.net/forum/...798#post148278
https://www.homemadetools.net/forum/...377#post200412
