Product name: Neck Curve Dial Meter Product function: This high-precision dial gauge measures neck deformation and bending, providing a reliable and clear standard for assessing neck flatness. It eliminates reliance on visual inspection, enabling accurate adjustments to correct neck curvature and improve instrument performance by reducing issues such as string breakage and noise. Instructions for use: Digital display advantages: Easy-to-read numerical output for quick and precise measurements. Pointer model advantages: Compact design and simple operation. 1. Begin by zeroing the gauge on a flat surface such as glass. Place the tool on the surface, loosen the screw in the upper right corner of the dial, rotate the large needle to zero, and secure it. For acoustic guitars, position the tool so the top rests on the 12th fret and the feet contact the frets on both ends. A negative reading indicates a concave fingerboard; a positive reading indicates a convex fingerboard. Adjust the truss rod in the guitar neck accordingly. Values closer to zero indicate optimal neck flatness. Digital models display readings numerically for enhanced clarity. For pointer-style models: Set the large needle to zero before measuring. First note the position of the small needle (main scale), then read the large needle (secondary scale). Each full rotation of the large needle advances the small dial by 1mm (one division). For example, if the large needle points to 9, the measurement is 0.09mm; if it points to 90, it is 0.9mm. The small dial indicates millimeters, with each division equal to 1mm. If the small needle reads 2 divisions and the large needle points to 43, the total measurement is 2.43mm. Size: 30x4x1.1cm Material: Metal Color: Black Package Contents: 1 x Neck Curve Dial Meter Note: Only the items listed are included. Lighting and display settings may cause slight variations between the product color shown and actual color. Measurement error allowance: +/- 1-3cm.