+1 on Sarafina's post - how to - but I did a modification to the ones I made by cutting a circle out of the bottom Sunbrella cloth of each bag. In this "hole" I sewed mesh
fabric (like that used on the bottom of
interior boat cushions). This allows any rain or
water that gets into the "bag" to exit through the bottom.
The tops of the bags are drawstring so I can tie them to the
lifelines or
rigging for
storage.
I had some left-over bags and found they were also great to store genoa/jib
sheets when the
boat is "in harbor" for extended stays. Since I have colored
sheets, the sun would bleach them too much unless I coiled the sheets and stored them in the bag which was then tied to the furled headsail.