Starting A Jam

A jam can start
when the referee has signaled that both teams are in the pack.
when the pivot man of each team is evenly together at the front of the pack.
when all jammers are at the rear of the pack.
when a pivot man from each team is on the pack the pivot skater cannot be more than 20 feet in front of the pack
when the jam starts.
The clock and the jam actually start when one of the jammers has been able to pass the leading opposing blockers in the pack.
Helmets must be worn by the jammers to score, unless through some involuntary action the helmet is knocked off, then the referee has the right to decide on this point.