Hair rollers are cylindrical tools used to create curls or waves in hair. They come in various sizes and materials, such as foam, plastic, or velcro, allowing users to achieve different styles. Hair rollers can be used on damp or dry hair and are often secured with clips or pins. To use hair rollers, sections of hair are wrapped around the roller and left in place for a period of time. This process helps set the hair into the desired shape. Once removed, the curls can be styled further with products like hairspray for added hold and definition.