During play, all the Blockers (including the Pivots) need to remain in close proximity on the track, in what is called the pack. The largest group of skaters, with skaters from both teams, skating in proximity to each other (defined as "within ten feet"—and yes, it is tricky to determine in the corners) is defined as the pack.
All action involving Blockers must take place within the pack, or up to twenty feet in front of or behind it (the engagement zone). If a Blocker falls behind or skates ahead, she is out of play and cannot engage any opposing players until she safely returns to the engagement zone. Blocking opposing players while outside the engagement zone results in a major penalty and a trip to the penalty box for that Blocker.
Jammers skate through the pack. The jammers' initial pass through the pack determines lead status. During subsequent passes, the Jammer earns a point for each opposing skater she passes. Jammers are allowed to engage each other anywhere on the track (regardless if they are in the engagement zone or not).
If the pack falls apart (due to skaters spreading out too far, etc.), the officials will call a no pack situation. At that time, the skaters must take action to reform the pack—skaters who skated ahead must slow down to allow the rest of the skaters to catch up (but need not skate "backwards"), and skaters who fell behind must speed up. If a skater does not take action to reform the pack, she may receive a penalty. Note: Jammers are not part of the pack, so in a no pack situation, a Jammer can still skate past her opponents and score points—and those opponents can get penalties for attempting to block her!