Your thinking of a washboard brother!!!
Ripped from Wikipedia;
The washboard and frottoir are used as a percussion instrument, employing the ribbed metal surface of the cleaning device as a rhythm instrument.
As traditionally used in jazz, cajun, skiffle, jug band, and old time music, the washboard remained in its wooden frame and is played primarily by tapping, but also scraping the washboard with thimbles. Often the washboard has additional traps, such as a wood block, a cowbell, and even small cymbals.
Conversely, the frottoir dispenses with the frame and consists simply of the metal ribbing hung around the neck. It is played, also with thimbles, but with much more strumming than tapping. The frottoir, also called a Cajun rub-board or Zydeco rub-board, is a mid 20th century invention designed specifically for Zydeco music. It was designed in 1946 by Clifton "King of Zydeco" Chenier, and fashioned by Willie Landry, a friend and metalworker at the Texaco refinery in Port Arthur, Texas. Clifton's brother Cleveland Chenier famously played this newly designed rubboard using bottle openers. Likewise, Willie's son, Tee Don Landry, continues the traditional hand manufacturing of rubboards in his small shop outside of Lafayette, LA.