Section 101(4)(b) in Delhi Motor Vehicles Rules, 1993
(b)The mark shall be kept clean and unobscured and shall be so fixed to the trailer that:-(i)the letter of the mark is vertical and easily distinguishable from the rear of the trailer;(ii)the mark is either on the centre or to the right hand side of the back of the trailer;(iii)no part thereof is at height exceeding four feet from the grounds; and(iv)the letter is eighteen centimeters in height and thirteen centimeters in width the stroke being four centimeters broad. The overall measurement of the mark is twenty centimeter high and eighteen centimeter wide.