Emery board in a dream is generally associated with the idea of achieving goals and success. Some people interpret that as the emery board in a dream represents personal growth and career advancements by polishing out your rough edges.
Emery boards are commonly used in nail salons to help give nails a smooth and shiny finish. They can also be used in a dream as an indication that the dreamer will have a smooth and successful life or career.
Also, using an emery board in dreams often symbolize physical resurfacing at significant steps or challenges. They could emerge when one has reached a turning point in life; when one discovers that progress has been undone through inaction; or at the start of a new journey.