This is question for mechanical/physical design. Not for code since according to my understanding code is protected by copyright. But for mechanical design, there isn't anything that has equal protection.
According to my understanding there isn't such thing as public patent. So how does anyone protect mechanical engineering design that is released to public use? According to my understanding anyone can pick that up and patent it for itself. It doesn't matter who invented it first, only who patented it first. Then nobody else can use that public design anymore.
As a side note, Chinese companies are patenting things that we are thinking as "public knowledge".
So how do I protect design that I want everyone to have right to use and prevent someone else patenting it to him/herself?