Millwrights build, assemble, maintain, and break down machinery. Due to their hands-on involvement with all aspects of machinery, millwrights have a strong understanding of how machines operate when they are in good working order and when they are in need of repairs. The Millwright Employers Association says that, historically, millwrights also completed carpentry duties. Modern millwrights use heavy-duty equipment and blueprints to assemble machinery used in assembly lines and manufacturing plants.