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The advice given on this site is based upon individual or quoted experience, yours may differ.
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It's called a jib bag or cover. The grommets go down to drain any water. You stuff (or fold) the jib, which remains hanked on to the forestay, into the bag and zip it up around the forestay. The clip attaches to the jib halyard, which you harden to lift the bag off the deck.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.