R.I. Gen. Laws § 5-20-24: License displayed in place of business — Advertising.

(a) In every place in this state within and from which a plumbing, irrigation, or commercial water-filtration/treatment business is conducted as specified for a master plumber, master irrigator, or master water-filtration/treatment-system installer, there shall be on display at all times a certificate of license as provided in this chapter.

(b) Any sign, listing, or advertisement of any type of a master plumber, master irrigator, or master water-filtration/treatment-system installer shall contain his or her name, address, and license number. This information shall be included on all trucks used by a master plumber in connection with his or her business.