The Turl knot is a classic knot used to tie the leader to salmon and steelhead flies on up or down eyed hooks (never straight eyed hooks).
This knot is widely used in Scotland and it brings the benefits that the leader will always sit straight and true to the fly ensuring the fly swings correctly. Similar knots to connect leader to the fly like the blood knot will sometimes shift around the eye therefore making the fly fish at an undesired angle.
The Turl knot or other loop style knots will always prevent this from happening. Useful Tip This is a great knot to use on larger hooks. We wouldn't recommend using on anything smaller than a #12, it possible but the knot must sit behind the eye. When tying flies always leave enough space between the head and the eye to tie the fly on using a Turl knot.