Section 205(a) in The Bihar Motor Vehicles Rules, 1992
(a)No load or other thing shall be placed on any motor vehicle so as at any time to mark or otherwise interrupt vision of any lamp, registration mark or other mark required to be carried by or exhibited on any motor vehicle by or under provisions of the Act, unless a duplicate of the lamp or mark so marked otherwise obscured is exhibited in the manner required by or under the Act for the exhibition of the mark or obscured lamp mark.
