+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
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.