Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition. A common way that these are depicted in a single scene is with one woman and two men performing together. Pornographic films or sex films are films that present sexually explicit subject matter for the purpose of sexual arousal and erotic satisfaction of the viewer. These scenes may either have the cameraman directly engaging in sex or merely filming others having sex. Hentai is the various forms of Japanese pornography, including H-manga, H-anime, and H-computer games. Masturbation has been depicted in art since prehistoric times and is mentioned and discussed in very early writings. Often a dominant woman, she may be called a Dom, Domme /ˈdɒm/, Femdomme, Domina, or Dominatrix, depending on context or personal preference. While most tentacle erotica is animated, hentai sex there are also a few live-action movies. Enema pornography involves adults given enemas to others, often fake. For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. Making a pearl necklace is one of the activities that sex workers use as safe sex alternatives for people who refuse to wear condoms. The related term twinkle-toes, which implies that a man is effeminate, tends to be used in a derogatory manner. Well-known female porn stars who expressed their pleasure in pegging their male partners include Taylor videos porno gay Wane, Debi Diamond, Brittany Andrews, and Monique Covét. The term is a slang word that originated in the momsex gay community and comes from the equestrian term bareback, which refers to the practice of riding a horse without a saddle.