Tentacle erotica can be consensual, but frequently contains elements of non-consensual sex. 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. The reverse of this, in which nude women interact with clothed men, is called Clothed male, naked female . Sigmund Freud considered foot binding as a form of fetishism. Hermaphrodite, also known as herm, refers to pornography, typically hentai, that features persons with the genitalia of both sexes. The Silent Duck, also called Duck-Billing, is the technique often used in which the person engaging in hand insertion shapes the hand to resemble a duck beak. There has been an increase in discussion and portrayal of masturbation in art, popular music, television, films, and literature. Examples of heterosexual pornographic film momporn series featuring creampies include Cream Filled Teens and Internal Cumbustion. Gay-for-pay describes male or female actors, pornographic stars, or sex workers who self-identify as heterosexual but who are paid to act or perform as homosexual professionally. Content featuring male bisexuality has been a growing trend since the advent of internet pornography. For instance, Amateur Allure has a trademark shot where the sexually performing cameraman circles a handycam around the sexually performing model head. There are number of types of sex parties: Swinger party/gathering A swinger party or partner-swapping party is a gathering at which individuals or couples in a committed relationship can engage in sexual activities with others as a recreational or social activity. Though there have been numerous gang bang gay hentai pornographic films since the 1980s, they usually involved no more than half a dozen to a dozen men. Sometimes one or more fingers may be inserted into the vagina to stroke its frontal gay bear porn wall where the G-spot may be located.