Why did free african americans need certificates of freedom?

Free Black people still faced danger. Many appeared in court to ask for a Certificate of Freedom. The claimant had to prove that he/she was born free or had been previously freed. If the court was satisfied, it would issue a certificate with a minute description of the person including skin shades, hair texture, and body scars. Freedom papers were essential for freedmen who wanted to travel, particularly those working on the rivers.