After a robust development process, you will eventually come to the point where you and your director agree that you have settled on your [best] solution to the design problem.
In some productions, especially commercial settings with high stakes and big budgets, there is an interim step between settling on the final design and presenting the final solution. For scenic designers, this takes the form of a white model, and for costume designers, this takes the form of detailed costume sketches. These are thoroughly assessed by the director, producers, designers and construction staff. After everyone’s concerns are taken into account, the designer proceeds with the final model and costume renderings.