A TAXI driver was threatened at knifepoint and his hands and legs were tied to the steering wheel by teenage robbers, a court heard yesterday. Store assistant Li Kwok-chi, 17, unemployed Choi Kam-wai, 15, and Yip Chun-lung, 16, pleaded guilty before Judge Hawkes to a joint count of robbery. Li was sent to a detention centre. Choi and Yip were given training centre orders. The District Court heard how they robbed Mr Chen Tong-seng of a pager, two car keys and $1,100 at Kau Lung Hang Shan, Tai Po, on January 23, 1992. Prosecuting counsel Mr Peter-Damien Cosgrove said that at about 1.55 am, five youths, including Li, Choi and Yip, boarded Mr Chen's taxi in Kowloon and asked to go to Kau Lung Hang. However, when the taxi reached Kau Lung Hang Village, two youths produced knives and demanded money. Mr Chen handed over his purse, and the youths tied him up. The driver struggled free and alerted police. Li and Choi were arrested after a nearby search and Yip was arrested later. Mr Terence Wai, for Li, urged the court to put his client on probation, adding that the defendant was a first time offender. Choi's counsel, Mrs Mahinder Panesar, said her client was remorseful. Mr Peter Wan, for Yip, said the defendant was serving a training centre order for another robbery.