In general, their criteria parallel those of the Supreme Court in sentiment. They include guidelines such as the amount of instruction, training, integration, use of assistants, length of professional relationship, regularity of work, location of work, payment schedule, source of funds for business expenditures, right to quit, and financial risk more typically seen with each work category. In their framework, independent contractors retain control over schedule and hours worked, jobs accepted, and performance monitoring. They also can have a major investment in equipment, furnish their own supplies, provide their own insurance, repairs, and other expenses related to their business. They may also perform a unique service that is not in the normal course of business of the employer. This contrasts with employees, who usually work at the schedule required by the employer, and whose performance the employer directly supervises. Independent contractors can also work for multiple firms, and offer their services to the general public.