Sail rigging

Question
Hi
My sail has two grommet holes at the clew for outhaul, what's the difference between the top one and the bottom one? When to use each one?  Thanks

Answer
It serves a couple of purposes.  If you use the top hole it will allow the bottom of the sail to get closer to the board and "close the gap" which will give you more speed.  If you rig it higher it will spill more air if overpowered.  If you are rigging your boom at lower part of the sail/mast opening it allows your boom to be more perpendicular when rigged. Try rigging and sailing on each setting to see what you like.