A temporary worker shows up at a warehouse, takes direction from a supervisor who does not employ them, and is paid by a company they have never visited. That arrangement is entirely lawful and it doubles the number of parties who can be liable for almost everything that goes wrong. This article explains joint employment — what it means, which of several tests applies to which statute, and why the same two companies can be joint employers for safety purposes and not for discrimination purposes. It explains the wage liability that follows a staffing client even when the agency was supposed to handle payroll, and the safety obligations that run to a host who controls the worksite. It covers workers' compensation exclusivity and the borrowed servant doctrine, which is the reason a temp injured by the host's negligence usually cannot sue the host. It covers day labor, professional employer organizations, and the conversion fees that make temp-to-hire arrangements contentious. It closes with what a staffing agreement should actually say and what each side should audit.