I was astounded to read
an article not long ago in "Good Old Boat" about the many ways people secure their sheets to a headsail clew. Many of the diagrams where quite complicated for what ought to be a simple task. If I recall the article accurately, it seemed to frown on the use of bowlines as they could flog themselves open in a blow. Yet in over 30 yrs of sailing, I've used bowlines for my headsail sheets almost exclusively and cannot remember one ever opening when I didn't want it to open. While they may hang up on the rigging (mine tend to hang up on a spinnaker pole fitting on the mast)now and then, virtually any knot/bend/or shackle would probably have the same tendency, particularly with an inner stay or baby stay which it must pass around. I've found that backing the headsail a bit prior to bringing it across the bow when tacking, releasing the old sheet crisply and cranking in the new sheet quickly, avoids many of these problems.As Ross and others mentioned, a buntline hitch is a great knot and one I really like, particularly for halyard shackles. But it also cinches up tight and that could be a problem with some kinds of clew cringles. It also makes them very hard to untie. One thing is for sure IMHO: I'll never use a metal shackle to secure sheets to a headsail. That is a sure way to get yourself hurt, or worse, if you ever have to go forward in a blow to deal with a flogging headsail.