Also known as the Double Uni Knot.
The Uni-to-Uni Knot is a basic bend knot for joining two lines of similar diameter together. The name leaves little to the imagination - two lines are joined together by two Uni Knots. When pulled taut, the Uni Knots apply opposing pressure on each other, and hold the knot in place. The use of Uni Knots to join the two lines allows the bend knot to maintain a low profile with a small diameter, and sail through the guides of a rod smoothly with little impact on casting distance.