What is the round disc at the end of a spinnaker sheet for??

This is not mine by the way.

I don't know for sure, but I'd guess the ring stops the shackle being pulled through the fitting on the end of the pole & getting jammed.
Someone here will know for sure.

It's generally on the spinnaker brace/guy (or sheet for boats with just sheets) that holds/stops the shackle from passing through the beak of the spinnaker pole. It will be on the kite side of the pole fitting allowing the pole to be winched aft...

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blindtadpole said..
It's generally on the spinnaker brace/guy (or sheet for boats with just sheets) that holds/stops the shackle from passing through the beak of the spinnaker pole. It will be on the kite side of the pole fitting allowing the pole to be winched aft...

Thanks

Makes sense now you have explained it.

What is the purpose for a rope on the center board housing on my sonata 6 ?

just guessing...... lifting the cover????