Masturbation involves touching, pressing, rubbing or massaging a person genital area, either with the fingers or against an object such as a pillow; inserting fingers or an object into the anus ; and stimulating the penis or vulva with an electric vibrator, which may also be inserted into the vagina or anus. It has been described as professionally hentai movies made porn which seeks to emulate the style of amateur pornography. Seconds after being deposited onto the face, the semen thickens, before liquefying 15–30 minutes later. Strappado with rope and a spreader bar. Common phrases used to refer to these individuals are chicks with dicks, trannies, or shemales, although these are generally considered pejorative slurs among transwomen. Given the wide range of practices, some of which may be engaged in by people who do not consider themselves as practicing BDSM, inclusion in the BDSM community or subculture is usually dependent on self-identification and shared experience. The term momsex also refers to the visible seeping or dripping of semen from the vagina . There are many other variations on male masturbation techniques. However, that term is usually applied to a male who observes somebody secretly and, generally, not in a public place. The anal and rectal tissues are delicate and do not provide natural lubrication, so they can easily tear and permit disease transmission, especially if lubricant is not used. In recent years, Japanese films of this genre have become more common in the USA and Europe although it still remains a small, fetish-oriented part of the adult film industry. However the genre remains a very small proportion of the pornographic DVD market; for example at porn retailer HotMovies. Female-to-male strap-on pornography became a popular sub-genre in the United States in the early 21st century, with a number of studios producing dedicated series about it. It can be gay boy porn combined with fellatio and the woman may move her breasts up and down on the penis for an additional stimulation, usually before the man reaches orgasm.