Insert the thick end of the string into the top of the bridge and thread it through until about 3 to 4 inches of the string stick out of the bottom.

Wrap the short end of the string around the long end of the string, creating a loop.

Pass the short end of the string through the loop (2 or 3 times for thick strings, 3 or 4 times for thin strings). Make sure the final pass leaves the string underneath the bridge.

Pull both ends of the string until the knot is tight.