In addition to petting and masturbation, there are two other ways of sexual relief that teenagers use to avoid an unwanted pregnancy or if they want to have an orgasm, when a sexual intercourse is not possible due to certain circumstances. Those are a vestibular intercourse and an intercourse between the hips.
The vestibular sexual intercourse (from the word vestibu-lum - the threshold, the vestibule of vagina in this case) is usually practiced as a way to avoid the hymen rupture (if a girl is a virgin), or to prevent an unwanted pregnancy. Penis is slightly squeezed between the vestibule of vagina and the pubis of a partner, with rhythmical motions until a male partner ejaculates.
The vestibular intercourse does not protect from sexually transmitted diseases or AIDS. This kind of intercourse can be used in the event of a weak erection, when it is hard or impossible to go inside. A male squeezes his penis in his hand, rubbing it against the vestibule of the woman's vagina.
Some women might like the excitement: the vestibular intercourse involves women's strongest erogenous zones - the clit, small lips of pudendum, the vagina entrance.
An intercourse between the hips is a friction of a penis between the hips of a woman. This act is used for similar purposes as the vestibular intercourse - to preserve the hymen and avoid a pregnancy. Mucous membranes of the genitals do not contact each other in this case, but it is possible to catch certain sexually transmitted diseases anyway.