Lyrics: Unknown
Music: Unknown
Two items put up for auction in 2026 contain references to this song. One is described as "A c. 1980s rehearsal folder used by Bob Weir while on tour" and includes "lead sheets and printed lyrics" for a number of songs including "Rusty Nail Blues (with the title handwritten at the top of the second page)". The other is described as a "collection of lyrics and lead sheets, used by Bob Weir while on tour c. 1991-1994". These include "copies of unique working lyrics for songs that were never fully finalized, such as ... Rusty Nail Blues."
It isn't clear whether this is an old blues song or a new lyric, or who the author was.