Line To Line Knot
Leader Knots and Knots that you can use to tie one fishing line to another line. The Blood Knot is tried and true and a long time favorite with fishermen. The Double Uni Knot is considered by many to be easier to tie and just as reliable. However, in multiple tests the J Knot is the line to line knot that comes out on top. Also the triple version of the Surgeon's Knot (wrap line three times through instead of two) is a guide favorite.
For joining leader to fly line, the Nail Knot is the knot you want. For joining backing to fly line or lines of different materials such as braid to mono, use the Albright Knot.