Some people get sexual pleasure by inserting objects, such as urethral sounds, into the urethra , a practice known as urethral play or sounding. They may regard it as an enhancing element of their sex lives or as their primary form of sexual activity. The term bondage describes the practice of Physical restraining. In the 18th and 19th centuries, some European theologians and physicians described it as heinous, deplorable, and hideous, but during momsex the 20th century, these taboos generally declined. Lolita pornography features women who are 18 years old or slightly older, who pretend to be underage teen girls. The most common male masturbation technique is simply to hold the penis with a loose fist and then to move the hand up and down the shaft. If one person is penetrated by two objects, it is generically called double penetration . This is commonly called double vaginal penetration or double stuffing. Both sexes sometimes apply lubricating substances to intensify sensation. Following the introduction of the Motion Picture Association of America film rating system, independent animation producers attempted to establish an alternative to mainstream animation. Shotacon : Similar to Lolicon, this genre involves prepubescent or under-aged boys between the ages 6–12. Biological anthropologist Helen B. Buttocks are sometimes emphasized in pornography, gay sex video where they are often referred to as booty. Detective magazines, comic books and early fetish magazines In the early 20th century, Detective magazines covertly provided a way of publishing bondage imagery. In the gay pornography industry, which uses amateurs as well as professional actors, the term gay-for-pay refers to actors labeled or believed to be straight but who engage in same-sex sexual activities for money. Use of the agreed safeword is seen by some as an explicit withdrawal of consent. In these research publications, it is suggested that real female ejaculation is the release of a very scanty, thick, and whitish fluid from the female prostate, while the squirting or gushing shown frequently in pornography is a different phenomenon, the expulsion of clear anime hentai and abundant fluid, which has been shown to be a diluted fluid from the urinary bladder.