I began using Blood Knots (also called Barrel Knots) when I was a trout fisherman and guide in the Rocky Mountains. I much preferred this connection to the Surgeons knot that many others liked. The Blood knot is a sleek compact knot that pulls straight and does not catch vegetation or the rod guides.
I use a standard blood knot for my trout fishing and any freshwater applications that I need to tie two lines together. I also use a blood knot for my permit, bonefish, redfish leaders for flyfishing or if I want to tie a leader onto monofiliment. For Tarpon fishing, we have to tie 2 different diameter lines together often and I like the 2 turn blood knot for that application.
All fishermen should know the blood knot as it is a great connection between 2 lines.
Here is how to tie the Blood Knot. If the video does not display, please click here
All the best,