Have you ever used a “wrest pin“?
I know I haven’t. Why you ask me? Well because I just found out what it is.
A “wrest pin” is used for stringed musical instruments like piano, harp, cello. The end of the strings are coiled and by which the instrument is tuned.
This is information comes from M-W’s Words-at-Play which is part of Merriam-Webster Dictionary.com