The defense area is divided into zones.
The 1st zone is the zone for the wings, the 2nd zone is for LB and RB and the 3rd zone is for CB and CR.
The players each defend their zone.
The player closest to CR automatically covers the attacking CR.
In the shown example CB covers the opponent's CR on the center and is counting herself as No. 3 from the left.
CB also counts herself as No. 3 from the right.

It is important that all the players inform each other by shouting, which attacking player they are covering.
The defense wing shouts "wing", the outer backcourt players shouts "back", the CB shouts "middle" and the center CR defender shouts "circle" or something else, which informs the other player who is taking care of whom.

If the attacking wing for example is running in without ball, the defending wing shouts "wing moving in" and follows the wing until she reaches her own defending backcourt.
Now the defending backcourt must cover the wing, as the wing is now in the second zone and the attacking backcourt is now the most outer player i.e. Wing and is placed in zone 1.
The backcourt is aware that the wing is coming because of the shout and is ready to cover the running in wing.
If the wing continues her running in, the backcourt follows her run until she reaches the CR.
The defender of CR then takes over and CB covers the attacking CR and so on

If the attacking wing is in possession of the ball, the defending wing moves forward and tries to stop her.
If the wing continues, no shift is made between the defending backcourt and wing.
The wing must not release the attacking wing until the ball is passed to another player.
When this happens, the wing moves straight backward in the defense and take the nearest position and undertake the role as defender of the zone, which has been entered.

If the CR accelerates, the defender of the CR shouts "circle moves" and follow CR to the nearest defending player.
If that happens to be the CB, then the CB becomes defender of the CR and "the old" defender of the CR becomes CB.
It is important that the defense is well aware about who is covering the CR all the time.

If the attackers perform a cross close to the defense, the defending player, who is covering the 1st crossing attacker, moves forward to cover/tackle the attacker.
The defender of the 2nd crossing attacker moves behind the 1st defender and is ready to move out and block/tackle the 2nd attacker.
If the cross is performed far from the defense, not switch is made.