An art assistant is someone who works with the art director and helps in drawing up layouts for the film or TV show. They mostly work from the pre-production stage and help the art directors in creating a perfect set. They are basically work for the art director and help out in the They work as runners for the art director and over look all the art work for the film or TV show. He/ she help in the making of the set and take specific measurements of the set props to replicate the same set for another scene later in the script.
They also work in collaboration with the construction studios and the production department. They usually work on a freelance basis for a film or TV show. Art Assistants work mostly to learn to become art directors and to learn new techniques from experienced art directors by working under them