Meaning: Rap your knuckles on wood to avoid bad luck.
Origin: It used to be thought that trees have good spirits and it was good luck to tap them to let the wood spirits know you were there.
The music that came to my mind from this pic was Don Mcleans - Vincent
This work belongs to 100 Days of Summer-project. It's an international project which provides its members from three continent with the opportunity to share their creative work within the intense framework of providing one artistic submission per day for 100 days.
This collaborative project is guided weekly by one expression or two, which may be used as a starting point for ideas. (The expressions come from the game cards of "The Origin of Expressions"). The provided information can be used any way one likes for example one can create literal or abstract interpretation of the expression etc. Everybody is also free to post independently of this structure.