Roller derby is a full-contact sport played on quad roller skates.
Two teams of up to fifteen players skate against each other on an elliptical track.
A game consists of two 30-minute halves, broken down into jams which last for no more than two minutes.
Teams field up to five skaters for each jam, four blockers and one jammer.
The jammer is the point scorer, whose goal is to fight their way through the pack of blockers in order to earn 'lead jammer' status. Once this is achieved, they then race around the track to do so again, scoring one point for each opposing blocker who they successfully pass.
Blockers are simultaneously playing offence and defence, aiming to help their jammer get out of the pack while also stopping the opposing jammer scoring points.
For more details on the rules of roller derby, check out the Women's Flat Track Derby Association website.