A woman in Montgomery County trying to take a mid-afternoon job break was attacked by a man armed with a knife who forced her into a residential backyard and raped her, police said Friday.

Shortly after 2:30 p.m. Thursday, police were called to the area of Colesville Road and University Boulevard West in Silver Spring. The woman, who works at a nearby shopping center, said the man approached her, struck up a conversation, pulled out a knife, and forced her into the nearby backyard, according to a police spokesman.

Police described the assailant as a black man, about 5-foot, 6-inches tall, with a medium build, gray and black facial hair and several missing or broken teeth.

Detectives ask anyone with information to call 240-773-5070. Those who want to be anonymous or be eligible for a possible reward of up to $10,000 can call 1-866-411-TIPS (8477).