Definitions for "Walk-Up"
Multi-story housing accessible only by stairs.
an apartment in a building without an elevator
a building with no elevator; "a walk-up apartment"
This is a type of establishment that is common in Soho (including Chinatown), A walk-up has an open door leading into a flat (or two or three) in each of which a prostitute works. They advertise mainly by means of a note by the entrance saying "model" and usually giving some details.
Keywords:  gunners, hunting, thrown, dog, heel
a trial test intended to simulate actual hunting: The handler, with dog at heel, judges, and gunners, all advance together in the field before the birds are thrown and shot.