The uni knot

The uni is one knot in two roles. On its own it fixes line to a hook or a swivel; tied facing itself, as a double uni, it joins two lengths of line. Which is why almost everybody who ties anything ties this one.

How it is tied

Pass the line through the eye, lay it back along the standing part and form a loop. With the tag wrap both strands, passing inside the loop — five or six turns for mono and more for braid. Then wet it, draw the turns up and slide the knot down to the eye.

The turns must lie in an even row, one beside the next. If they have crossed, the knot is retied.

The double uni for joining

Lay the two lengths parallel and facing, and with each tie its own uni around its neighbour. Then pull on both standing parts, and the knots slide together and lock against each other.

That is how a main line is joined to a leader — quickly and without any special skill.

How many turns

The rule is simple: the slipperier and finer the line, the more turns. On heavy mono extra turns stop the knot seating; on fine braid they have to be added.

Its other names

The knot is known as the uni knot in North America and as the grinner in Britain, while its sliding version is called the Duncan loop. It is one and the same tie: the names came from different traditions, not from different knots.

Worth knowing because of search: most of the diagrams and video sit under one name or the other.

A loop knot from the same tie

If the knot is not drawn down against the eye but left a few millimetres short, you get a loop in which the lure swings freely. That is wanted for light plugs and flies, whose action a rigid attachment kills.

Under load such a loop closes up — which means that after a serious fish it has to be retied or it stops being a loop knot at all.

When it loses

A double uni comes out bulky. If the join has to run through the rod rings on every cast, it knocks and costs distance.

For that case there are flat friction knots — chiefly the FG, used to join braid to a fluorocarbon leader. They are slimmer, but they take practice and patience, and tying one in the wind is hard.