Modern roller derby is an international, full contact, amateur sport. It is played by two teams of fourteen. Five members of each team are on the track at any given point. Game play consists of a series of short matchups (“jams”) in which both teams skate in the same direction around an oval designate with a player (the “jammer”) scoring points by lapping members of the opposing team. The teams attempt to assist their own jammer while hindering the opposing jammer.
Roller Derby is played on a (usually flat) oval track. A match is called a ‘bout’. Each bout lasts for two periods of thirty minutes each. Within these periods there are multiple point scoring opportunities, known as ‘jams’. Each of these can last up to 2 minutes.
At the start of the jam, four players from each team line up on the pivot line (this is the first starting line on the track) all together in a pack. These are the blockers. One of these blockers from each team will be wearing a stripe on her helmet. They are the pivots. It is their job to direct their blockers and try and control the speed of the pack.
One player from each team will be line up on the jam line (this is the second starting line on the track and is behind the pivot line and the pack), these are the jammers. They will be wearing stars on their helmets. They are the point scorers.
When the whistle blows, the pack will start to skate (maybe fast, maybe very slowly, depending on tactics) and the jammers take off and try to make their way through the pack as quickly as possible. The first jammer to make it through the pack without committing any penalties (no elbows to the face etc) becomes lead jammer for that jam. All that means is that she has the right to call off the jam, whenever she wants. If neither jammer makes it through the pack legally there is no lead jammer and the jam must go on for the full two minutes.
On their second pass through the pack, the jammers can score points. They score one point for passing the hips of each opposing blocker. Therefore, in one pass, the maximum points they can score is four, unless they also lap the opposing jammer, which is a grand slam, and score five points.
Therefore, the blockers job is to help their own jammer get through the pack, while hindering the other team’s jammer from getting through, effectively playing offense and defense at the same time.