Counterweight and Flap

I walked along the apartment baseboard out into the quiet entry hall to inspect the brass mail drop slot on the door. The flap rested shut at a ninety-degree angle. I approached the lower rim, planted both feet firmly against the door frame, and pressed upward with one hand. The hinge offered moderate spring resistance before yielding. I wedged a small rubber doorstop corner under the lip to test its holding capacity, then slowly released my grip. The brass plate settled snugly against the rubber edge, suspended four centimeters open. System held steady.