Bukkake pornography usually depicts numerous men having sex with one woman, with multiple, usually 10 or more, men ejaculating on the female face. Such momporn films continued to be produced but could only be distributed by underground channels. Various groups within society have considered depictions of a sexual nature immoral, labeling them pornographic, and attempting to have them suppressed under obscenity and other laws, with varying degrees of success. POV pornography involves camera angles designed to provide the viewer a view similar to that seen by one of the participants, whose face is never shown. To tea bag is a slang term for the sexual act of a man placing his scrotum in the mouth of a willing sexual partner for pleasure or onto the face or head of another person. Making a pearl necklace is one of the activities that sex workers use as safe sex alternatives for people who refuse to wear condoms. Unlike Yaoi, Bara is normally made by actual homosexual men, for homosexual men, and tends to focus on the more realistic obstacles and challenges that come with being homosexual in Japan. The Japanese sex industry uses the hentai sex term Paizuri . Sadomasochism does not imply enjoyment through causing or receiving pain in other situations . The principal characteristic of voyeurism is that the voyeur does not normally interact directly with the subject of his/her interest, who is often unaware of being observed. In September 2003 the BBC reported on the new dogging craze. The higher pay scale and profile within a production often leads to group scenes where a straight actor only tops. In many cases, that person is also aroused by smelling body parts that have a urine scent. One or more of the participants may engage gaysex in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. Japanese rope bondage is distinguished by its use of specific katas and aesthetic rules. Erotic literature and pornographic films have been devoted to the sexual uses of glory holes.