As purebs posted, the Uni-knot is good for a substitute blood knot to connect the leader to the shock tippet too, or use a double surgeons loop to double surgeons loop connection. The uni-knot is easy to tie on a fly with 18" of 25 lb. shock for the toothy feeders. For more bites in very clear water drop down to 18" of 20 lb shock tippet; just be prepared to lose a few more flies!