Tigers of this version had two headlamps on the top front corners of the hull. They were relatively fragile and were not needed for battle, therefore they could be removed and stored inside the tank.
When you unscrew this type of headlamp, this sturdy socket remains on the vehicle.
But Border's instructions do not explain that. Instead, Border suggest that the entire headlamp system - lamp, socket and wiring duct - is "optional". Their instructions further compound this mistake by depicting the finished hull with none of these parts on it.