Here's another simile so obscure Wiki doesn't even have a page on it: the blue line. In business a project manager might use it like this:
"The bean counters at corporate thought they could kill off my project, but I had a buddy in Procurement who showed me a blue line right through the middle of 'em."The blue line is a critical element behind successful stealth-bomber missions. I was briefed about it while visiting Whiteman AFB to write about the B-2 bomber. (I had the chance to climb into the rather compact flight deck; here's a link to a 360-degree cockpit view on the Air&Space/Smithsonian website.)
When Lockheed began working up stealth technology (a combination of cunning geometry and a low-reflective skin) in the late 1970s, proponents believed that no radar could pick out such a plane; ergo, the plane could fly just about any route during night.
But a more skeptical look at its radar signature suggested, and the shootdown of an F-117A during a mission over Yugoslavia in 1999 by a well-commanded SA-3 battery proved, that this wasn't a safe assumption. Planners had to acknowledge that no solid object can be totally invisible to radar all the time, particularly when painted from ahead or behind.
An important part of the solution was to work out specific approach and departure routes with the lowest likelihood of detection, based on measured characteristics of the adversary's air-defense network.
This is the blue line. I'm not sure of the name's origin but it might be because Lockheed's original project name for stealth technology was Have Blue.
The blue-line database to each major target must be assembled well before the shooting starts, then updated rigorously.