Wash. Rev. Code § 76.36.090
A person desiring to use a catch brand as an identifying mark upon forest products or booming equipment purchased or lawfully acquired from another, shall before using it, make application for the registration thereof to the department in the manner prescribed for the registration of other marks or brands as herein required. The provisions contained in this chapter in reference to registration, certifications, assignment, and cancellation, and the fees to be paid to the department shall apply equally to catch brands. The certificate of the department shall designate the mark or brand as a catch brand, and the mark or brand selected by the applicant as a catch brand shall be inclosed [enclosed] in the letter C, which shall identify the mark or brand as, and shall be used only in connection with, a catch brand.
RCW 76.36.090