The surgeon’s join knot (as differentiated from the surgeon’s loop knot) is important for anglers to know because it can join two lines of moderately different diameters. The smoother (and ultimately better) knot in this category is the blood knot. But the blood knot can be more challenging to tie, especially in bad weather and/or with cold fingers, etc. The surgeon’s join knot is illustrated online at Master it and the next time you need to tie two lines together you’ll do it like a pro.