Gamut's Tying Strings / Changing Strings section has guides on tying different types of strings for different purposes:
Tying String Knots - to hold the string onto the instrument's tailpiece
Tying a String-Leader - additional, thinner lengths lengths of gut tied at one end of a string
Tying Viol Frets - viol family of instruments
Tying Lute Frets - lute family of instruments
Tying Tail Gut on Historic Instruments - the Stradivari Stitch

