Scrapheap Challenge is a British television show where teams of contestants build a working machine that can do a specific task, using materials available in a scrapyard. The series features teams of four or five members who are given ten hours (based around sunset) to build vehicles or machines to complete a specific task, such as a trebuchet, or complete a racecourse whilst acting as a gyroscope. The programme ran for eleven series and was originally shown on Channel 4. The format was exported to the United States, where it was known as Junkyard Wars. The US show was also produced by RDF Media, and was originally shown on The Learning Channel. Repeats have aired on another Discovery network, the Science Channel.