Cal. Code Regs. tit. 13 § 1247
The lower half of the fifth wheel on any truck, tractor, or dolly shall be securely attached to the frame by nonwelded U-bolts of adequate size or other equally effective means. Capscrews and bolts used to secure the fifth wheel to the vehicle frame shall meet SAE Standard J429 for Grade 5 threaded fasteners in the 1965 or any later edition of the SAE Handbook, and shall be installed so that the frame will not crack, warp, or become deformed. Positive means shall be provided to prevent the lower half of the fifth wheel from shifting on the frame to which it is attached. Locking devices on a sliding fifth wheel shall have sufficient strength to control the gross weight of the vehicle or combination of vehicles being towed. All fifth wheel components shall be maintained in good condition.
Cal. Code Regs. Tit. 13, § 1247