Felching is a sexual practice involving the act of orally sucking semen out of the vagina or anus of one partner. For a foot fetishist, points of attraction include the shape and size of the foot and toes , jewelry , treatments , state of dress , odor, and sensory interaction . The warm sensation felt when urine trickles on the body seems to give very relaxing and pleasurable feelings to the person. Female masturbation involves the stroking or rubbing of a woman vulva, especially her clitoris, with an index or middle fingers, or both. Preggo pornography features pregnant performers and may include erotic lactation as a fetish. A scene where many women have sex with one man is referred to as a reverse gang-bang. This is commonly called double vaginal penetration or double stuffing. Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black descent are promiscuous, and their buttocks are objectified by porn as a result. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Some are aroused from hentai movies wetting their diapers, others like mature milfs messing their diapers. The consensual submission of the submissive is sometimes demonstrated to others by symbols indicating his/her belonging to the dominant, such as wearing a collar, special tattoos, piercings, a very hot gay sex short haircut or a bald head. Cartoon pornography includes, but is not limited to, hentai and parody renditions of famous cartoons and comics. Although there may be no connection between coprophilia and sadomasochism , the limited data on the former comes from studies of the latter. Lying face down one may use the hands, one may straddle a pillow, the corner or edge of the bed, a partner leg or some scrunched-up clothing and hump the vulva and clitoris against it. To avoid soreness from this resulting friction, some may prefer to use a personal lubricant, masturbation cream or saliva during masturbation.