46 CFR § 45.33
Diamond
April 15, 2021
(a) Each vessel must be marked with the diamond mark described in figure 2 of §45.35 amidships below the upper edge of the deck line on each side with the center of the loadline mark at a distance below the deck line equal to the summer freeboard assigned under this part.
(b) The width of each line in the loadline mark must be 1 inch.