Pound A Beat Meaning

(idiomatic, usually of a police officer) To walk a regular route.

Example: 1948, Alfred Haines Cope, The administration of civil service in cities of the third class in Pennsylvania, page 65
  Flat feet may be important to the patrolman who must pound a beat, but in cities with patrol cars, should mild cases of flat feet disqualify?
1970, The Bench and Bar of Minnesota, Volume 27, Page 8
  You can't ask a college graduate who is interested in law enforcement to pound a beat for four years before he becomes a sergeant.
2012, Frank Kane, Grave Danger, section 14
  I worked my way up from a flatfoot pounding a beat to where I am today. I like being a cop, I'm proud of being a cop.