Transsexual porn star Wendy Williams has stated that transsexual Porn is classified as Straight Specialty. Mammary intercourse is a sex act, performed as foreplay or as non-penetrative sex, that involves the stimulation of the male penis by the female breasts and vice versa. As a result, little in history was documented to give an accurate description of how female homosexuality is expressed. Other objects such as ball momsex point pens and thermometers are sometimes used, although this practice can lead to injury and/or infection. Tentacle erotica can be consensual, but frequently contains hentai porn elements of non-consensual sex. There is no singular or archetypical behavior; therefore, a wide range of thought patterns and behaviors exist, but all tends to be a harmless and efficacious release from some kind of pressure. Bondage websites and bondage imagery in mainstream pornography As of 2003, specialist bondage magazines were mostly displaced by the availability of bondage material on the World Wide Web, and the presence of bondage imagery in mainstream pornographic magazines such as Nugget gay sex video and Hustler Taboo magazine. Since the 1980s, many practitioners and organizations have adopted the motto safe, sane and consensual, commonly abbreviated as SSC, which means that everything is based on safe activities, that all participants be of sufficiently sound/sane mind to consent, and that all participants do consent. Detective magazines, comic books and early fetish magazines In the early 20th century, Detective magazines covertly provided a way of publishing bondage imagery. The genres of pornography are based on the type of activity featured and the category of participants, for example mateur pornography is a category of pornography that features models, actors or non-professionals performing without pay, or actors for whom this material is their only paid modeling work. There may be more than two participants; both group sex and gang banging can be included. Depictions of male and female masturbation are common in pornography, including gay pornography.