A TEENAGER who raped a young woman in a vicious gang sex attack after she was abducted at knifepoint and knocked out with chloroform acted out of a desire to save face, the High Court heard yesterday. Tam Chun-ho, then 18, claimed he raped the woman because he did not want to lose face after winning a ''cloth-scissor-stone'' game to determine who should go first. He was sentenced yesterday to 61/2 years' jail. Prosecutor Philip Cantrill told how the 21-year-old nightclub hostess was seized from behind as she walked home along the Castle Peak Road, Tuen Mun, shortly before 1 am on October 1, 1991. Her assailant held a knife to her throat and marched her along the street to the other youths. Her bag and valuables were seized, the court heard. The gang then took her to a deserted building site where one of the teenagers covered her nose and mouth with a rag soaked in chloroform, causing her to black out. Mr Cantrill said: ''The youths intended to rape and sexually abuse the girl and administered the chloroform in order to overcome her resistance. ''Once she had collapsed the youths carried her to a grassy area and proceeded to rip her clothes off. ''One of the youths then suggested they all play a game known as the 'cloth-scissor-stone game' and that the winner abuse the girl first. ''The defendant won the game. ''He then proceeded to rape the unconscious girl.'' Other gang members then took it in turns to rape and indecently assault the girl. The victim began to come round in the middle of her ordeal, but feigned unconsciousness fearing what might happen if she did not. The gang only stopped when they were scared off by the sound of a police siren. The woman was treated at hospital for bruising, cuts and a chemical burn to her face. Defence counsel Lambert Lee said Tam, who admitted rape and robbery, believed he would ''lose face'' if he did not rape the woman after winning the game. Passing sentence Deputy Judge Burrell told Tam, now 21: ''These are offences of the utmost gravity. ''The ordeal to which you subjected the victim will remain in her memory forever.'' Tam, who was only arrested last year, was sentenced to 51/2 years for rape and four years for robbery to run partially concurrent, making a total of 61/2 years. Ng Yuk-hung, 17, and Tsoi Man-chun, 17, were sentenced to 11 and 10 years respectively after they were convicted of rape and robbery following a High Court trial earlier this year. Leung Yu-wing, 16, was sentenced to five years for robbery after his rape conviction was quashed and Chung Yau-tat, 17, was jailed for four years after admitting robbery and giving evidence against his accomplices. Chu Kwok-wai, 16, who admitted robbery and attempted rape, was jailed for seven years.