https://www.albanycountyfasteners.com/Fastener-Drives-Heads-and-Threads-s/1132.htm
https://www.youtube.com/watch?v=smExyKMfiIE
sketching_nuts_and_bolts.pdffasteners.pdfScrews_Lesson.pdfsketching_nuts_and_bolts.pdffasteners.pdfScrews_Lesson.pdf