Most artistic and craft based occupations require you build a portfolio of your work. You need this so employers and clients will be able to see the quality of your design and/or construction work before they hire you. A portfolio is there to show the employer/client your aesthetic abilities, your range of styles, and demonstrate your ability to present and organize your work product. In broad general terms this applies for all artistic professions, regardless of type. You can learn about the specifics of your particular skills in later pages, but here you can view the following videos, PDFs and web pages that show a small sample of the wide assortment of theatre jobs that require portfolios: