I agree that clients unknowingly will shop plans from another shop. I also know that some builders will knowingly shop drawings by cutting of title blocks and other identifying markings. I get around most of this by adding a big fat ugly non removable water mark diagonally across the drawing with the company name. They can then shop but the other timber frame company's will know where the drawings came from and can call. IF I get a set of timber frame drawings from a prospective client and know or feel that they belong to another company I call them and ask if #1 if the client ones the rights to shop around or #2 can they buy the rights. If the answer is no then I tell them that we can design a frame from scratch using our own design ideas or they can go somewhere else. Most folks are understanding and are grateful that they are dealing with a company with ethics. One of our competitors ended up in a law suit over copyright issues. I don't know how it ended up but I'm sure that is was expensive after the lawyers were finished.