There are 2 teams of five skaters. Each team consists of 1 Jammer (the star), 3 Blockers and 1 Pivot (the stripe). The Blockers and pivots form the Pack. Jammers have to make their way through the pack and then on their second attempt and future attempts they get a point for every opponent they pass. All while the other team's blockers are trying to stop them.
A bout consists of two 30 min. halves. A jam can last up to 2 minutes each. If a jammer makes their way though the pack on the first run through without committing a penalty, they will have Lead Jammer status. The lead jammer can call the jam off.
This is not the roller derby of days gone by. Players cannot grab, pull, elbow or trip one another.
They also can not block from behind, clothes-line or head-butt.
Breaking any of these rules can lead to being sent to the penalty box or expulsion.
FULL CONTACT SPORT
Roller derby is a full contact sport requiring safety gear.
Injuries can and do happen.
Spectators should also be aware - as track-side seating is for 18+ only.
Flat track derby action may extend outside of the track boundaries.
Roller Derby overview - Derby 101 - Courtesy of WFTDA.com