Organization:Make trios.1 trio is on field A and 1 trio on field B.On both fields one trio is on reserveTrainer with the balls is on field B.
Execution:Tr. "serves" the ball to field A: pass-set-up-attackOn field B the ball is defended and caught in max 3 contactsBall is placed in the ball pitAfter the service pass the trio runs on to field B and becomes a reserveThe trio on field A becomes a reserve on field A.Immediately after the action the reserve trios enter the field.
Expanding:Now 2 trios on field BLoop becomes: fitting trio becomes blocking trioBlocking trio becomes defending trioThe defending trio becomes reserve on field AThe reserve on field A passes and attacks