The phrase "to build a prototype" means to create a preliminary version or sample of a product or idea to test and improve it before making the final version. Full definition
In his free time, at school and at home, this student built a prototype of a shelter on a robotic base that could drive itself. (edutopia.org)
3D printers can be used for building prototypes for the medical, aerospace, engineering and automotive industries, and the more compact units are priced for consumers. (ces.tech)
At this point, the startup is looking for funds to prove its concept, and that money can be helpful in building a prototype. (microventures.com)