As a piano technician many people ask me about how to keep the dust off of the soundboard on their grand piano. This is a tool designed specifically to use to clean the soundboard on a grand piano. There is a slot in one end of the flat steel that you can put a soft rag through. The tool is flexible so that you can push the rag around underneath the strings to remove the dust.
A microfiber cleaning cloth can be added to this item for an additional cost.