Disclosed are guitars having neck structure with distinct longitudinally spaced apart substantially transversely extending thumb receiving notches formed inclined to the flat neck front surface to lie side by side in the back surface thereof. The thumb receiving guide notches are disclosed arranged for both flamenco and/or popular music guitarists. The thumb receiving guide notches serve inter alia each of the following functions: both as a sight and feel guide for aiding a guitar player in learning and ascertaining the proper longitudinal placement of his hand along the guitar neck as he repositions his hand up and down the guitar neck while playing the guitar; as a thumb stop which aids the guitarist in stopping with precision his hand movement up and down the guitar neck and to quickly and surely regrip the guitar neck; as hand positioning guide which in the case of a flamenco guitarist disciplines the guitarist to maintain proper hand position; and as a thumb pivot surface which aids playing the guitar. For the purpose of teaching a person to play a guitar, numerals or other identifying marks may be placed in the thumb guide notches to further visually aid the person in the correct positioning and repositioning of his hand along the guitar neck.