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 and Hustler Taboo magazine. Use of the agreed safeword is seen by some as an explicit withdrawal of consent. A study of the condom usage habits of New Zealand sex workers said that they milf fuck offered various safe sex alternatives to vaginal sex to clients who refused to wear a condom. Some pornographic films use an artificial semen substitute to simulate or enhance creampie shots. Evolutionary psychologists suggest that rounded buttocks may have evolved to be desirable trait because they provide a visual indication of the woman youth and fertility. In POV porn, the shooting style is generally similar to gonzo pornography, with the person receiving sexual gratification holding the camera him or herself—aiming it down at the actress or actor who is performing the sex act. Spanking can be administered in a number of spanking positions. These are often fake. Multiple men and women Bisexual pornography features one woman and two men who all perform sex acts on each other. If one person is penetrated by two objects, it is generically called double penetration . To avoid soreness from this resulting friction, some may prefer to use a personal lubricant, masturbation cream or saliva during masturbation. 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 gay cock in same-sex sexual activities for money. For example, in Australia it is rated Refused Classification . Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on hentai movies which it concentrates, and not necessarily on the market to which each sub-genre appeals. 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.