This paper discusses the role of prototypes with special focus on rapid prototyping or also called additive manufacturing. The authors of the paper combine literature on additive manufacturing and boundary crossing to increase the understanding about prototypes and specifically rapid prototyping during new product development. This paper is cross-disciplinary and aims to fulfil three objectives: (1) Synthesis of literature regarding potential role of prototypes to support crossing of the knowledge boundaries during new product development; (2) Outline of prototypes' properties that enable them to become boundary objects; (3) Outline meeting points between boundary crossing literature and the literature on additive manufacturing which can provide guideline for further investigation. The authors have found that the concept of boundary objects is still underdeveloped in the context of additive manufacturing, as the main benefits are related to quality, time, and cost. Through combination with literature on boundary objects, the role of prototypes to converge different diverging perspectives, translate and transform knowledge are emphasized and underlined.