The Silent 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. Masturbation is the self-sexual stimulation of the genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. Common positions include lying on back or face down, sitting, squatting, kneeling or standing. It is used, for example, at fertility clinics to stimulate sperm donors. Rape pornography features performers simulating rape. Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime . Biological anthropologist Helen B. Some straight actors have started acting in gay porn only to be accused of being gay while others first step was to strictly do solo scenes. Mammary intercourse is known as titty-fucking, titfuck, or a titjob in the United States, as well as tit wank or French fuck in the United Kingdom - the latter term dating back to the 1930s; while a more jocular equivalent is a trip down mammary lane. Some men also anime hentai enjoy anal stimulation, with fingers or otherwise, without any prostate stimulation. The other person may do the same during or big tit milf after. Femdom features BDSM scenes in which the dominant partner is female. Today, religions vary in their views of masturbation; some view it as a spiritually detrimental practice, some see it as not spiritually detrimental, and others take a situational view. Preggo pornography features pregnant performers gaysex and may include erotic lactation as a fetish. The term pearl necklace is used by some because the drops of semen deposited by the man resemble a necklace of translucent white pearls. Clothed male, naked female is one-sided female nudity in which one or more females are nude while one or more men are clothed.