Men may also rub or massage the glans, the rim of the glans, and the frenular delta. This makes varying degrees of stimulation an integral part of oral sex for many men. The term is typically used by the cinematographer within the narrative framework of a pornographic film, and since the 1970s has become a leitmotif of the hardcore genre. The strategies and tactics that are used to smuggle one of the couple into and out of the toilet undetected are as important or almost as important as the urination. When the interest in a particular subject is obsessive, the behavior may be described as stalking. Most bisexual porn is made by small hot gay sex production companies rather than the major studios. In Japan, point of view pornography is referred to as hamedori . The niche popularity grew significantly in the latter half of the first decade of the 2000s. Examples of heterosexual pornographic film series featuring creampies include Cream Filled Teens and Internal Cumbustion. Bondage/BDSM Bondage pornography features performers tied up or constrained in various ways. Content featuring male bisexuality has been a growing trend since the advent of internet pornography. People may experience pleasure from anal sex by stimulation of the anal nerve endings, and orgasm may be achieved through anal penetration – by indirect stimulation of the prostate in men, indirect clitoral/G-spot stimulation in women, and associated sensory nerves . Bondage websites and bondage imagery in mainstream pornography As of 2003, specialist bondage magazines were mostly displaced by the availability of bondage material on the World Wide Web, and the presence of bondage imagery in mainstream pornographic magazines such as Nugget and Hustler Taboo magazine. The Silent milf fuck Duck, also called Duck-Billing, is the technique often used in which the person engaging in hand insertion shapes the hand to resemble a duck beak. The name was coined from the lesbian hentai title of the controversial book. However, various groups within society considered such depictions immoral, labelling them pornographic, and attempting to have them suppressed under obscenity laws, with varying degrees of success.