Paul, former Navigator sailor and now a Pathfinder sailor, and I have been talking about the rigging of Pathfinder sails. The most recent question was about how to tie the mainsail to the mast. I use a what I think of as a slight variation of the lover's knot (which I have also heard called a fisherman's knot).
The true lover's knot is basically two interwoven overhand knots. I refer to the knot I use as a variation because the overhand knots are not interwoven, but really back to back as you will see in the photographs below.
(Disclaimer: I am not a knot guy. I know just two or three knots and probably do not tie those the correct way, but they work for me. )
The sail ties, short bits of line, stay in the mainsail's grommets, a loose overhand knot on one end and I-don't-know-what on the other end (right side in the photo above), just a quick turn of the line to give it some bulk to it doesn't slide throughout the grommet and fall out.
With the boom and gaff mounted on the mast, I use one hand I undo the I-don't-know-what and pass the line through the center of the existing overhand knot.
And then tie the second overhand knot. Simple enough, right? Yes, it is simple but I've seen several people struggle with this knot, the direction of the second knot being the problem. Practice a few times and it becomes obvious.
The two overhand knots, in my version, should rest neatly back to back. I can tie it in about two seconds without looking.
For me, it is a good general purpose knot. The main is held on the mast with this knot, the mizzen is on the mizzen mast with this knot, the head of the main is tied to the gaff with this knot and the gaff jaws are tied to the mast with this knot.
And just as easy as it is to tie the knot, it is easy to untie.
Maybe not the best knot or the "traditional" knot, but it works for me.