It happened on the B3081 near Verwood - he had to be cut free by firefighters.
Teenager Robbed At Knifepoint
Detectives in Bournemouth are appealing for witnesses and anyone with information to come forward after a boy was robbed in the Southbourne area of the town.
The incident took place just after 10pm on Wednesday 18 July 2012 on Southbourne Road.
The victim, a 17-year-old boy from Bournemouth, was walking with friends when he was approached by a man who asked for a cigarette and some money for mobile phone credit.
When the victim refused, the offender threatened him with a knife and stole a black iPod Nano.
Fortunately, the victim escaped without injury.
Detective Constable James Batty, of Bournemouth CID, said:
"The victim and his friends have obviously been left very shocked by this incident, and we are very keen to trace the offender.
"The victim has described the suspect as a white man, around six foot tall, of slim build with short ginger hair.
"He was wearing a tracksuit top and bottoms with black stripes down the sides.
"I am looking for any members of the public who may have witnessed this incident to come forward, or anyone who may have information regarding the identity of the offender, to contact Dorset Police in confidence."
Witnesses and anyone with information should call Dorset Police in confidence on 101 quoting incident number 18:511. Alternatively, call the free and anonymous Crimestoppers line on 0800 555 111 where mobile phone tariffs may apply.
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