In the fetish cuckolding subculture, it is most common for the female to take on the sexually dominant role and the male the submissive role, however, female subs, sometimes referred to as cuckqueans, also exist. This type of pornography is almost exclusively hentai, as true hermaphroditic humans are not fertile and are not usually found in nature. 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. Some people get sexual pleasure by inserting objects, such as urethral sounds, into the urethra , a practice known as urethral play or sounding. Common positions include lying on back or face down, sitting, squatting, kneeling or standing. Other fetish Bareback pornography features performers who are not wearing condoms. In S/M, the Sadist is usually the Top and the Masochist the Bottom, but these roles are frequently more complicated or jumbled . Solo pornography recognized with AVN Awards include the hot gay sex All Alone series and All Natural: Glamour Solos. Behind the Green Door was one of the first pornographic films to feature sex between a white actress with a black actor . Works in this genre may be considered adult for any number of reasons. When used as an alternative to penile-vaginal penetration, the goal may be to preserve virginity or to prevent pregnancy. Foot fetishism has been defined as a pronounced sexual interest in the feet or footwear. Fisher said that perhaps, the fleshy, rounded buttocks attracted males during rear-entry intercourse. Boots are seen as the perhaps most fetishistic of all footwear and boots may be the most popular fetish clothing attire. However, bisexual pornography is often placed near the gay section in adult hentai sex video stores, since many consumers are gay men. Women with women Main article: Lesbianism big tit milf in erotica: Lesbianism in contemporary pornography Lesbian or girl-girl pornography features women engaged in sex together, but is typically aimed at a male audience.