An 18-year-old woman was left unconscious after being assaulted by a man on a footpath in Dewsbury.
Detectives today released details of the "terrifying" assault, which took place in Thornhill at around 11.30pm on June 10.
The woman was walking along a path off Grange View, which is known locally as 'The Tops', when she was approached by the attacker.
She was left with a head injury and was taken to hospital for treatment.
Detective Constable Nicola Keitch, of Kirklees Safeguarding Unit, said: "This was a terrifying incident for the young woman, one which left her with a head injury and incredibly distressed.
"I am hoping to speak to anyone who was in the vicinity at the time, who may have witnessed anything, or recognise the description of the suspect.
"If anyone has any information, I would urge them to come forward to speak to the police."
The attacker was described as a white man, aged around 50 to 60 years old, and of medium build, with a receding hairline at the front and shaved at the back.
He was wearing jeans, a green jacket and some glasses.
The man was also walking a white and black dog, similar to a spaniel, which was off the lead at the time.
Anyone with any information about this incident is asked to contact Det Con Nicola Keitch via 101, quoting crime reference 13170263043.
Alternatively, information can be passed to independent charity Crimestoppers anonymously on 0800 555 111.