What are the "reference points" in order to hit the correct notes in double bass technique? Of course, I realize that first you have to get the open strings in tune, and then you have the natural harmonics of the 4th, 5th, and octave intervals and the help of placing the thumb in the crook of the neck for that position. I heard that Edgar Meyer had little metal circles installed in the neck of his bass to help him from playing sharp in the upper register. However, the contract I have for the bass I am renting forbids placing any tape on the bass. Since the double bass strings are so long and the instrument has no frets, what other ideas do people here have in order to have reference points for good intonation?