Was it common for 12th century cities to have guards on every corner, with full armor, just standing there to 'guard'? How common was this?

by Nibby2101

I am watching the movie 'The kingdom of Heaven' and I see guards everywhere. In palaces, on the street, in houses, courtyards, you name it. Was this common in the 12th century or is it just made up by the movie? Thanks in advance!