Utah Code § 41-3-504
Special plates -- Display.
Special plates issued to dealers, dismantlers, manufacturers, remanufacturers, and transporters for the purpose of operating or moving motor vehicles on the highway under the provisions of this chapter shall be: (1) prominently displayed on the rear of the motor vehicle where clearly visible; (2) free from foreign materials; (3) clearly legible; and (4) securely fastened in a horizontal position.