Original equipment devices with nonadjustable housings shall be mounted for the photometric test at the same angles at which they are mounted on the vehicle. Aftermarket devices with nonadjustable housings shall be mounted with the base on a horizontal or vertical surface, whichever is appropriate, unless different mounting instructions are included with each device offered for sale.
Cal. Code Regs. Tit. 13, § 657
Note: Authority cited: Section 26103, Vehicle Code. Reference: Sections 24012 and 26103, Vehicle Code.