Well, this is posted under Catalina 310. The usual connection is a ring on the tack, and a hole in the drum. The boat is not here, which is why I am asking for the owner. I was depending on some owner being close to their 310 or have pics.I guess you looking for a Wichard twisted D shackle such as the ones form West Marine: WICHARD Stainless Steel Twisted D Shackles | West Marine
Boat model and a photo of the attachment points might help.
Nope. Wouldn't work. The furler is built with a 5/16" hole for the pin if a shackle.You could also use a soft shackle.
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Make your own for about $2. The cost of the dyneema line with 2-3 times the working load of a D shackle.
This one has an estimated 10,000 lb working load. Material cost $3.50.