33 CFR § 401.11 - Fairleads.
(a) Mooring lines shall:
(1) Be led at the vessel's side through a type of fairlead or closed chock, acceptable to the Manager and Corporation;
(2) Pass through not more than three inboard rollers that are fixed in place and equipped with horns to ensure that lines will not slip off when slackened and provided with free-running sheaves or rollers; and
(3) Where the fairleads are mounted flush with the hull, be permanently fendered to prevent the lines from being pinched between the vessel and a wall.
(4) When passing synthetic lines through a type of fairlead or closed chock acceptable to the Manager and the Corporation all sharp edges of the fairlead, closed chock and/or bulwark shall be rounded to protect the line from chafing or breakage.
(b) Wire lines shall only be led through approved roller type fairleads.