Interest in BDSM can range from one-time experimentation to a lifestyle. The fundamental principles for the exercise of BDSM require that it should be performed with the informed consent of all involved parties. In the 1920s, Havelock Ellis reported that turn-of-the-century seamstresses using treadle-operated sewing machines could achieve orgasm by sitting near the edge of their chairs. Also see POV. Fisting may be performed with or without a partner. Teacher and Student or Boss and Secretary pornography involves sexualized situations which take place between an authority figure, such as a teacher or boss, and an underling, such as a student or secretary, often fake. However the genre remains a very small proportion of the pornographic DVD market; for example at porn retailer HotMovies. A large part of the popularity of these videos is seeing how regular gay bear porn and normal the girls are in real-life. Kinbaku is a Japanese style of bondage or BDSM which involves tying up the bottom using simple naked milf yet visually intricate patterns, usually with several pieces of thin rope . Japanese rope bondage is distinguished gay hentai by its use of specific katas and aesthetic rules. There are no particular or preferred elements within maiesiophilia that are common to all maiesiophiliacs. Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition. For other diaper fetishists, simply wearing a diaper, the bulking feeling and crinkling sounds associated with it, is enough to cause the fetishist a form of erotic pleasure or sexual arousal. Solo pornography features performers masturbating. In many cases, that person is also aroused by smelling body parts that have a urine scent. The essence of voyeurism is the observing but may also involve the making of a secret photograph or video of the subject during an intimate activity.