Copyrights protect "expressions" of works of authorship, not ideas or product designs. Your data sheet can be copyright protected, and your user manual, your photos and videos of your great thing also. The name could be protected by trademark. If someone makes the same knife and called it something else and writes their own ads and takes their own pictures you have no protection.

Not all works of "authorship" are copyrightable subject matter. Is the knife a statue ?
![enter image description here][1]

There is a form of patent called a design patent that does cover the "look" of an article of manufacture. It has to be a novel and non obvious look.


  [1]: https://i.sstatic.net/YEboQ.jpg