The correct functioning of the details depends on the proper work during this stage of development. The design process includes several steps. The required inclinations of the surfaces are applied, while the overly thick areas are modified and thinned. The construction of the assembling parts also happens here, and it has to comply with the purpose of the final product. Seals, sockets, and ducts that have to be moisture- and waterproof are also being created at this stage to provide a higher level of durability. The design needs to fit into the ideas of ergonomics, and this is a part of the process too.