Abstract: A metallic anti-intruder type gate, particularly adapted for use in windows offering access to a fire escape. The gate includes an outer frame element permanently installed within a window frame, and a hinged gate element supported by the frame and maintained in locked position relative thereto by a sliding bolt. The door is formed to include a rectangular peripheral frame and metal lattice which avoids adequate ventilation and light consistent with mechanical strength. The sliding bolt is shielded to permit access thereto for operation only from that side of the door facing the interior of the building in which it is installed.