Compared to other instruments that create sound via string, classical guitar has more performance techniques in terms of number and variety. The reasons behind this variety lie in guitar’s structure and repertoire. In consequence, finding new performance techniques or (when needed) creating them had been a vital matter for classical guitar performers. In classical guitar, fretting with left hand thumb enables performers to have a larger sound range and more polyphonic possibilities compared to traditional performance techniques. The explanation of the technique is done under individual titles according to their difference of application. In every title, the application of the technique is explained with examples from parts of music pieces. Other potential uses and long term effects of the technique are also mentioned.