Another auction option TradeYard claims that it is the largest single source of used heavy equipment online and available for purchase. More than 100,000 pieces of used equipment are listed at www.tradeyard.com, including tractors, graders, ditchers, loaders, skid steers, trailers, off-road trucks and even generators and air compressors - all available for bidding. The auction house offers a call center staffed by people who know equipment.