A bout consists of two thirty-minute periods made up of a series of plays or “jams.” Each team may field a roster of up to 15 skaters but can send no more than five on the track for each jam. They play one of three positions: Blocker (there are three), pivot (marked by a stripe on their helmet) or jammer (marked by a star on their helmet).
Each jam starts with a whistle. The first jammer to skate through the pack earns the title of “lead jammer” giving them the advantage of calling off the jam whenever they wants by placing their hands on their hips and waving them up and down.
Both jammers work to lap the pack a second time to start accumulating points. Each opposing player they pass legally and in bounds is worth one point, including the opposing jammer. When the lead jammer calls off the jam — or when the maximum time of two minutes have passed — the jam stops and the officials calculate the scores.
Jammers do not get points for passes in which they commit a penalty. The most common penalties in derby are back blocking, going out of bounds to cut the track, blocking too far from the pack (out of play), elbowing (chicken-winging), tripping (low blocking) and clothes-lining (multi-player blocking). Infractions result in a penalty only if there is an impact on game play, for example, an opponent is caused to fall. Penalties result in a skater spending one minute or more in the penalty box.
