The most common male masturbation technique is simply to hold the penis with a loose fist and then to move the hand up and down the shaft. New York photographer Irving Klaw also published illustrated adventure/bondage serials by fetish artists Eric Stanton, Gene Bilbrew, Adolfo Ruiz and others. Real school shots or videos which are sexualized may violate privacy laws in some countries. Some masturbate only using pressure applied to the clitoris without direct contact, for example by pressing the palm or ball of the hand against underwear or other clothing. Older names for a pornographic film include stag film, and blue movie. Ass to mouth is a slang term primarily used to describe the withdrawal of a penis from the receptive partner anus followed by the immediate insertion into the receptive partner mouth. The act may be carried out face to face, or head to tail, with the woman recommended to be on top if she has smaller breasts. On the other hand, the masochist enjoys being hurt, humiliated, or suffering within the consensual scenario. It is typically animated pornography, as the legal age to be featured in a pornographic film in Japan is 18. The warm sensation felt when urine trickles on the body seems to give very relaxing and pleasurable feelings to the person. In humans, females generally have more round and voluptuous buttocks, caused by estrogen that encourages the body to store fat in the buttocks, hips, and thighs. This type of pornography is almost exclusively hentai, as true hermaphroditic humans are not fertile and are not usually found hot gay sex in nature. As a form of non-penetrative sex, it can be milf fuck done for its own enjoyment or as foreplay. Most bisexual porn is made by small production companies rather than the major studios. Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black descent are promiscuous, and their buttocks are objectified by porn as a result. It is geared towards heterosexual men, who most typically lesbian hentai define a threesome as such.