A model maker is a professional craftsperson who creates a three-dimensional representation of a design or concept. Most products in use and in development today first take form as a model. This "model" may be an exacting duplicate (prototype) of the future design or a simple mock-up of the general shape or concept. Many prototype models are used for testing physical properties of the design, others for usability and marketing studies. Mock-ups are generally used as part of the design process to help convey each new iteration. Some model makers specialize in "scale models" that allow an easier grasp of the whole design or for portability of the model to a trade show or an architect or client's office. Other scale models are used in museum displays and in the movie special effects industry. Model makers work in many environments from private studio/shops to corporate design and engineering facilities to research laboratories.