String players are used to intonating their pitch by ear relative to other pitches they are playing, however when you take up a fretted instrument, pitch becomes absolute.  This takes the guess work out of finger placement on the fingerboard, but without properly intonating, you'll find even well-tuned open strings impossible to play in tune on across strings and up the fingerboard! In the short video below, EVS Shop Foreman Ted Hardin demonstrates the procedure for intonating a fretted violin (in this case, a 7-string Wood Violins Viper) by comparing the harmonic pitch to the fretted pitch at the 12th fret and adjusting the bridge angle to compensate for the difference between treble and bass strings. http://www.youtube.com/watch?v=s4zEssohr7o