Female masturbation involves the stroking or rubbing of a woman vulva, especially her clitoris, with an index or middle fingers, or both. Although there may be gay movies no connection between coprophilia and sadomasochism , the limited data on the former comes from studies of the latter. Special forms include erotic roleplay like ageplay, in which a difference in age, either real or enacted, formulates the background; or petplay. This genre also features male-on-male fellatio through a small hole made in a bathroom divider. A smotherbox gives a more dramatic experience . In the West, masturbation in private or with a partner is generally considered a normal and healthy part of sexual enjoyment. Some pornographic films use an artificial semen substitute to simulate or enhance creampie shots. Additionally, the buttocks give an indication of the shape and size of the pelvis, which impacts reproductive capability. When used as an alternative to penile-vaginal penetration, the goal may be to preserve virginity or to prevent pregnancy. During anal sex, male pleasure can be particularly derived from the prostate, which can lead to an orgasm and ejaculation. By comparison, anime hentai gonzo pornography puts the camera right into the action, often with one or more of the participants both filming and performing sexual acts, without the usual separation between camera and performers seen in conventional porn and cinema. The queening stool is also related to a smotherbox, which also allows the person under the seat to be locked in place, restrained by the neck as in a set of stocks. This is commonly called double vaginal penetration or double momsex stuffing. Its gain in prominence has been attributed to its depiction in the film Pecker, which was released in 1998. A woman can use a secondary vibrator, between the dildo and her genitals, to get pleasure from pegging. These actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. As the prostate is touch-sensitive, some directly stimulate it using a well-lubricated finger or dildo inserted through the anus into the rectum.