The original meaning of the ‘fatal funnel’ was a warning to ensure that you did not pause or remain in doorways or windows. It was to prevent silhouetting yourself there. Of course, when readying to prevent a room entry, the ‘bad guy’ will naturally set up to shoot towards natural entry points. So, rather than over-defining the ‘fatal funnel’, as the video says, it is more about enemy lines of fire, corners, and avoiding silhouetting yourself there. Don’t try and define the ‘funnel ‘ geographically and over complicate it, creating a whole bunch of stylized drills based on over-complicated assumptions about the fatal funnel.