This guide covers auctions, consignment, and secondhand commerce from formation to title. Part I explains auction formation, reserve, and the conditions of sale that displace default rules. Part II covers the buyer's premium, disclaimers, and authenticity warranties. Part III covers consignment, the security interest problem, and artist consignment statutes. Part IV covers title: voidable title, void title, and entrustment. Part V covers provenance, authenticity, and cultural property. Part VI covers pawn, estate sales, and vehicle auctions. Part VII covers judicial, bankruptcy, and tax sales. Part VIII covers the consumer protection overlay, online platforms, cash reporting, and dispute resolution.