I know I have partly answered my own question here but would appreciate other peoples opinion on the subject. From day one I have struggled to tie a shock leader knot. I have tried several different knots including an allbright knot and knot that is a combination of a granny knot on the shock and a uni knot on the main line. My problem is the main line snaps at the knot when I test it. I have a very high failure rate and have come to the conclusion it is due to the knot strength of my main line (Challenge 15lb with a 60lb Challenge shock leader) I put plenty of spit on the knot to lubricate it but still it often snaps. The most annoying thing is it fails more when out and don't need the aggravation of knot failures. I have tested my knots with amnesia line and my 60lb shockleader and they are OK. I have just bought a new spool of line (Ultima) and it appears better but still fails sometimes hence my conclusion of the knot strength of the my other line. Does anyone else have the same problem or can anyone offer advice how to get round this. Will buying the best line possible solve my problem?