My grandfather was a NYC cop - back in the day. (He died years before I was born so this is third-hand.)
They used to lock up "the bums" over the winter to get them dried out, out of the cold, and three hots and a cot.
Per DF, if DGF saw a "bum" acting up during the warmer weather, he could whistle for him. The threat was "Joe, if you make me chase you, I'm not taking you in come winter."