N.D. Cent. Code § 47-20.1-10: Minimum corner requirements

The registered land surveyor establishing or rehabilitating corner markers shall place as a minimum acceptable marker, a durable ferromagnetic monument not less than eighteen inches [45.72 centimeters] in length and not less than one-half inch [12.7 millimeters] in sectional dimension driven to a survey elevation depth to which is affixed a cap bearing the center point and the registered land surveyor's certificate number firmly impressed thereon.