I have two mouthpieces that have unusual shapes/size that I couldn't find a ligature that fit well. I read about "string ligature" and tied a few and loved how they worked. The only things I didn't like about them is that you can't fit a cap easily (for my alto I have to use the cap from a bari to fit over the ligature). Once i got one tied just the way I liked it, I used hot melt glue on the outside of the tied side leaving the strings free where they hold the reed to the piece -- that way I can slide it off and on without having to retie it every time.
Here's a picture of an alto string ligature I made for an odd size alto piece
Here's a picture of an alto string ligature I made for an odd size alto piece
