When joining two sections of monofilament or gelspun lines, or when adding a mono leader to gelspun, the Uni-to-Uni Knot is a popular choice. The lines don’t have to be equal diameter, but the connection is strongest when the lines are not of dramatically different diameters; such as 12- to 20-pound mono to mono, or 15-pound gelspun to 30-pound mono leader.
The number of wraps is important. Make five wraps with mono, five to ten wraps with gelspun. When connecting dissimilar line diameters, use fewer wraps on the larger diameter line. Properly draw down the knot by pulling on the running and tag ends of each line separately, then pull both running lines to firmly seat the knots against each other.
Lay the two lines alongside one another and form a loop in one of the lines.
Make five to seven turns through the loop and around both lines.
Pull the tag end and the running line to draw down the loop, but do not completely tighten it.
Make a loop in the other line, make five turns and draw down.
Pull on both running lines to slide the two tightened loops together.
Firmly pull on both tag ends to completely draw down both Uni Knots, then trim the tag ends.