A Hull Identification Number (HIN) is a unique 12-digit number assigned to vessels by the manufacturer. It’s what distinguishes vessels from each other, much like a Social Security Number or a Vehicle Identification Number. All vessels must have an assigned HIN in accordance with Federal Regulation, Title 33 CFR 181, Subpart C. Understanding the Hull Number Format U.S. §181.25 explains that hull numbers are to be 12 characters long with no spaces or hyphens. Manufactures must assign the...