If you make them for anyone else--either a commissioned work or as part of your employment--the rights (title and copyright) belong the person or business paying you for the project. (They would be "works made for hire.") You can't get any title over another person's property.If you make them for yourself, they belong to you--until and unless you later sell them, at which time they physically belong to the person you sold them to, though the terms of sale can let you retain copyright. (If they do, make sure there is something in writing stating that you retain copyright.) We are not sure what you mean generally by a "certificate of title" since most things that a person owns--e.g. jewlery, electronics, furniture, clothing, artwork they puchased, etc.--does not in fact come with a "certificate of title" and with only a few exceptions (e.g. cars, houses) there is no need for title to something you own.