Double the main line. Overlap the heavy leader and form the familiar Uni-Knot circle. Go around the strands and through the circle with the doubled end three times. Now, slip your finger into the loop. Holding all strands on the other side of the knot with the left hand, pull the loop with your finger until the knot is very snub.
A. Tie another Uni-Knot with the end of the heavy leader around both strands of line. Again, only three turns are required. Pull the second knot down snug.
B. Slide the knots together by pulling with opposing pressure on the main strand of leader and both strand of main line. Continue until no slippage is felt.
C. For final tightening, you will probably have to grip the line with a full hand grip, instead of using thumb-finger grips. This tie will consistently provide close to 100% of line strength if the first Uni-Knot is snugged completely tight, and if final tightening is done carefully and with steady hard pressure.