Lebeau gives rules for the corner on page 144
CORNERS - DEEP 1/3 BUT NO 2 TO 1 READ
ENABLES CORNERS TO GET TIGHTER ON #1 RECEIVERS (ALERT STACK OR SLASH RELEASE)
SEAM PLAYERS WILL CARRY SEAMS TO FREE SAFETY
NO CHINA CALLS IN FIRE ZONE
The Corner is playing a very aggressive technique on the #1 receiver's route. The only route the corner is not aggressively playing is when the #1 receiver releases on a shallow crossing route. In that case the Corner will work the Deep 1/3 divider and squeeze to a vertical by the #2 receiver.
The Corners must be alert for reduced splits that might result in the #1 receiver going on a fast crossing route. With the Seam player carrying #2 vertical the Corner is not required to midpoint 2 vertical is his zone as he would in a traditional Cover 3 Deep 1/3. This allows the Corner to play press or bail technique on the #1 receiver and does not require the Corner to make a "China" call vs. smash route concepts. Overall the concept is very simple; the corner plays #1's route aggressively unless it is a shallow crossing route.
The play of the Middle 1/3 or FZ Middle player as Lebeau calls it is very similar to a traditional Cover 3 middle 1/3 safety. The safety will work the middle 1/3 divider (imaginary line that cuts the middle 1/3 in half) and expect the Seam players to carry and deliver vertical routes. The FZ Middle player will midpoint 2 verticals and squeeze to 1 vertical route in the middle 1/3.
The FZ Middle player does have to be aware of the release of the #3 receiver. If the #3 receiver releases out the FZ Middle player must lean to #3 because the Seam player will go with the flat route and the 3RH player will not stretch vertically.
The Fire Zone coverage concept allows for many of the benefits of man free coverage while still utilizing zone coverage concepts.