must be PERMANENT!
Putting them on the mast is not sufficient! All a thief needs to do to remove this identification is peel the numbers off, or for that matter, remove the mast.The Documentation number must be marked as follows (quoted from USCG Vessel Doc. web-site)"The official number assigned to documented vessels, preceded by the abbreviation "NO" must be marked in block-type Arabic numerals at least three inches high on some clearly visable interior structural part of the hull. The number must be permanently affixed so that alteration, removal, or replacement would be obvious and cause some scarring or damage to the surrounding hull area."I have seen boats that have the number carved into a teak plank that is screwed and glued to a stringer, bulkhead, berth face, or the inside of the hull. Many boatowners apply stick-on letters to the inside of the hull and then lay a thin layer of wetted-out fiberglass over the numbers to make them permanent. Many sailboats have this number located on the hull inside a cockpit locker.But whatever you do, they MUST be PERMANENT.I have included a link to the "frquently asked questions" page of the USCG Documentation web-site.