Tying lute frets
Hold the instrument in some way that it is secure and will not slip around as you work on it. This could be on a table, or, perhaps you can hold it between your knees. Remove the old fret by clipping the knot with some fingernail clippers. Replace only one fret at a time.
Tie the new fret a little down the fingerboard from its home position, (toward the nut). The fret will be pulled up into position. This will help hold the fret tightly on the fingerboard.
Thread one end of the fret material under the strings and around the back of the neck as in figure A. The long end we will call strand 2 and the short end we will call strand 1. Pull strand 1 behind strand 2 for a length of two or three inches as in figure A.
Make a loop around strand 2 with strand 1 by pulling it around strand 2 and underneath itself as in figure B.
Pull the knot tight. You may have to rotate the fret on the neck a little so that the knot lies more or less at the joint of the fingerboard and the neck. Use the other frets as a guide.
Now, make a simple overhand knot by looping strand 1 and strand 2 around each other as in figure C.
Pull the knot tight again.
Clip the ends so there is about 1/8 inch of each end sticking out of the knot. Use a small flame or soldering iron to burn the ends of the strands down to the knot. Be careful not to burn the knot or the instrument!!
Pull the fret up into position. You can usually tell where the fret goes by the marks and wear on the neck.