I had one on a center line that I worked on for about 20 minutes last night. Chewed on it and worked on it gently with a needle to open it up a bit and it finally came out. Didn't think it would, but keep working it and they all come out eventually.

This post is about a cure, and yes i'd endorse the "tap with a hammer" method. Prevention is good too, I was once told that most knots tend to be towards the line ends, as when rigging the lines bunch together and the ends can spin round on themselves and make a loose knot that will then tighten. Since then I have carefully paid attention to this and have managed to nip a few potential knots in the bud.

So they should come out with flavored lines. I'll take cherry centerlines please !