Inverted string nut for zero-fret guitar systems

A string nut body configured for mounting on a guitar neck adjacent to a zero fret, the guitar neck terminating in a headstock carrying a plurality of tuning machine posts, the string nut body comprising:

• a plurality of downward-facing tunnels, each tunnel having a first opening facing the zero fret and a second opening facing a corresponding tuning machine post on the headstock,
• each tunnel configured to receive a guitar string extending from the corresponding tuning machine post, through the tunnel, across the zero fret, and along the length of the guitar neck,
• each tunnel configured such that the string forms a first bend over the zero fret and a second bend within the tunnel, the second bend being oriented opposite to the first to reinforce string stability and downward pressure on the zero fret,
• each tunnel further configured to maintain lateral spacing of the strings across the zero fret and to guide the string along a controlled path,
• a solid, curved roof over each tunnel configured to guide the string and facilitate sliding without frictional sticking, and
• a mounting structure configured to secure the string nut body to the guitar neck adjacent to the zero fret.