46 C.F.R. § 169.721 – Storm sails and halyards (exposed and partially protected waters only).

(a) Unless clearly unsuitable, each vessel must have one storm trysail of appropriate size. It must be sheeted independently of the boom and must have neither headboard nor battens.
(b) Each vessel having headsails must also have one storm head sail of appropriate size and strength.
(c) Each vessel must have at least two halyards, each capable of hoisting a sail.