The Calgary Roller Derby Association! We

Roller derby takes place on an oval track, with two teams sending five players each onto
the track — three blockers (defence), one pivot (last line of defence) and one jammer
(scorer). Helmet covers are used to display the players' positions: a striped cover is used
for pivots, a cover with two stars is used for jammers, and no cover is used for blockers.
Pivots and blockers from both teams start the game by forming a single pack. The two
jammers, who are not considered to be part of the pack, are positioned 20 feet behind
on the start line. The referee signals the start of jam formation by blowing a whistle. On
this first whistle, the blockers begin moving counter-clockwise around the track. Once
the last blocker in the pack has passed where the front of the pack was initially lined up,
the referee blows the whistle again, and the jam begins!
A jam is a 2-minute countdown period during which both teams attempt to score points.
Points can only be scored by the jammers who attempt to pass the pack and lap around
as many times as possible. After passing the pack in a legal manner the first time,
jammers earns one point for each time they pass an opposing blocker/pivot. During a
jam, all pivots/blockers must remain in the pack. If a pivot/blocker falls or otherwise
becomes separated from the pack, she is out of play (i.e., cannot block or assist the
jammers) until she catches up to the pack.
The first jammer to pass all pivots and blockers cleanly once the jam begins wins the
status of lead jammer for the remainder of the jam. The lead jammer controls the play
and can end the jam at any time before the 2 minutes are up by placing her hands on
her hips, signalling the referee to officially call off the jam. To impede the progress of
the opposing team's jammer, players may block using body parts above the hips,
excluding hands and head. Penalties are given to skaters who block illegally (elbow, trip,
clothes-line, grab, or pull skaters down), fight, behave in an unsportsmanlike manner, or
otherwise break the rules.
A roller derby game is called a bout, and consists of two 30-minute halves. In each half,
as many two-minute jams as possible are played.