The attack was the first of two robberies on the same Halifax street in two days and police believe they were both carried out by the same pair of thugs.
Officers are appealing for witnesses to the incidents in Wainhouse Street, King Cross, to come forward and have issued a description of a woman they are keen to speak to.
The first robbery took place at 3.45pm on Monday as a 14-year-old boy finished his round.
Two men approached the youngster and threatened him, putting him in a headlock, before stealing property from him.
The second attack occurred at 5pm on Tuesday as an 18-year-old man returned home from Calderdale College, Halifax. He was also threatened with violence and belongings were taken from him.
This robbery was witnessed by a young woman but she left before police could speak to her. They are keen to trace her. She is described as white, slim, with short blonde hair and wore a pink top.
The first suspect is described as Asian, between 5ft 10in and 6ft tall, of stocky build, in his early 20s, with short black hair and facial hair.
The second is described as Asian, between 5ft 10in and 5ft 11in tall, slim to medium build, with black hair and facial hair.
Both wore black tops and black trousers.
Anyone with information should call Detective Sergeant Ross Wadsworth at Halifax CID 01422 337085 or Crimestoppers anonymously on 0800 555 111.