In modern BDSM vernacular, the queening stool allows open access to the crotch while seated. Celebrity sex tapes are amateur or professionally-made recordings of sex acts, as performed by a celebrity and their partner. Jerk off instruction features a performer encouraging or instructing the viewer to masturbate, often culminating in a countdown at the end of which the viewer is invited to induce orgasm. It is used, for example, at fertility clinics to stimulate sperm donors. Though there have been numerous gang bang pornographic films since the 1980s, they usually involved no more than half a dozen to a dozen men. Sadomasochism is practiced in isolation relatively rarely, though some masochists report biting, pinching, or even stun-gunning themselves as a prelude to, or as part of, masturbation. Common positions include lying on back or face down, sitting, squatting, kneeling or standing. When the interest in a particular subject is obsessive, the behavior may be described as stalking. Real medical shots or videos may violate privacy gay black porn laws in some countries. Kinbaku means tight binding Kinbaku-bi which literally means the beauty of tight binding. Actual spying may violate privacy and/or trespassing laws in many countries. The term combines elements of the Freudian psychoanalytic fetish and the Marxist commodity fetish, and is used in the context of British, Spanish and French colonialism and imperialism and their aftereffects. For circumcised males, on whom the glans is mostly or completely uncovered, this technique creates more direct contact between the hand and the glans. Individuals are also sometimes abbreviated when referred to in writing, so a dominant person may be referred to as a Dom for a man, and a Domme for a woman. The concept of lesbian, to differentiate women with a shared sexual orientation, is a 20th-century construct. Rainbow party A rainbow party is an urban legend spread from the early 2000s. Pegging is a sexual practice in which a woman performs anal sex on a man by penetrating the man anus with a strap-on dildo.