Shower curtains are used in bathtubs with a shower or shower enclosures and are usually made out of vinyl, cloth or plastic. Shower curtains have two main purposes: provide privacy and prevent water from flooding the bathroom. Shower curtains usually surround the bath inside the tub and are held up with railings or curtain rods on the ceiling. To accommodate the different types of bathtub shapes, railings can come in different sizes and are flexible in their design. Many people use two shower curtains, one that is inside the tub that can be purely functional or can be decorative as well, and an outer shower curtain, which is purely decorative.