46 C.F.R. § 45.127

For the purposes of this part—

(a) Position 1 means in an exposed position on—

(1) The freeboard deck or a raised quarter deck;

(2) A superstructure deck or a trunk deck and forward of a point 1/4L from the forward perpendicular; or

(3) A trunk deck whose height is less than Hs.

(b) Position 2 means—

(1) On a superstructure deck aft of a point 1/4L abaft the forward perpendicular; or

(2) On a superstructure and trunk combination, that is Hs or more n height, aft or a point 1/4L abaft the forward perpendicular.