Ah I now see what you mean The link is put in incorrect Frith used an instrument with a locked 3rd bridge in the middle I saw this before on wiki but it has been deleted I can t find it on internet anymore sorry It must be in some of his cd booklet I suppose The only thing I can t find is that he used homemade instrument but I can t find an explanation of how it looks like The Elgart Yates only mentions the technique not the words 3rd bridge page 4 by pinning it between a string and the nut fretboard soundboard or saddle of the guitar If you have a better word than extra bridge please replace it I don t know how to call it else