For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. These scenes may either have the cameraman directly engaging in sex or merely filming others having sex. A sub-set of vaginal fisting attempts to photograph the female cervix immediately after the fist is removed from the now-gaping vagina. A common way that these are depicted in a single scene is with one woman and two men performing together. This industry hentai movies employs thousands of performers along with support and production staff. Comic books often featured characters being tied up and tying others up, particularly in damsel in distress plots. The buttocks in human females thus contain more adipose tissue than in males, especially after puberty. The gay twink porn reverse of this, in which nude women interact with clothed men, is called Clothed male, naked female . Some BDSM practitioners prefer a code of behavior that differs from SSC and is described as risk aware consensual kink , indicating a preference for a style in which the individual responsibility of the involved parties is emphasized more strongly, with each participant being responsible for his or her own well-being. The term soft crush refers to the more common fetish surrounding videos involving inanimate objects or small invertebrates being crushed, while the term hard crush refers to such videos involving larger animals with vertabrae, and arguably more pain-susceptible animals . In some scenes or relationships it may be impossible for consent to be withdrawn in the middle of a scene, or the bottom may have the ability to revoke consent for a relationship as a whole, but not for a particular scene. This fetish sometimes originates from childhood memories of needing, or of seeing another needing, to urinate. A facial is a form of non-penetrative sex, though it is generally performed naked milf after some other means of sexual stimulation, such as vaginal sex, anal sex, oral sex or masturbation.