Function:

The single fisherman's knot is used to join two ropes of different diameters or materials.

Precautions:

When the diameter or material difference between the two ropes is small (within 3mm), the single fisherman's knot can be used. It can also be used on ropes of the same diameter or material. Note that both ends of the rope should have about 10 cm of tail left to prevent the knot from coming loose due to tightening under load.