Noun
rubboard (plural rubboards)
(music) A scraped percussion instrument used in zydeco music, resembling a washboard but without a frame, generally hung around the neck.
Clifton's brother Cleveland Chenier famously played this newly designed rubboard using bottle openers. Source: Internet
Conversely, the frottoir (zydeco rubboard) dispenses with the frame and consists simply of the metal ribbing hung around the neck. Source: Internet