This is a very old and universal bend. It’s used often on board, even if it is not always very solid. It serves to knot together two ropes, even if they have different thicknesses. It’s also called the becket bend or weaver’s knot.
STEP 1
Make a bight with the first rope, shown here in yellow. Using a second rope, pass it under the bight and then behind the two strands.
Finish by forming a loop with the running end that passes under itself. There should be a strand of the running end that comes out below the standing end, while the other strand comes out above the standing end. Gently pull the four strands to tighten the knot.