Product name: Neck Curve Dial Meter Product function: This high-precision neck flatness dial meter measures deformation and bending of the neck, providing a reliable and clear measurement standard for assessing neck alignment. It eliminates reliance on visual inspection, enabling accurate adjustment of neck flatness to help reduce issues such as string breakage and noise. Instructions for use: Digital display advantages: Easy-to-read data with clear numerical values. 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 the base at 0. For wooden guitars, position the top at the 12th fret, ensuring the feet at both ends rest on the frets. A negative reading indicates a concave fingerboard; a positive reading indicates a convex fingerboard. Adjust the truss rod in the neck accordingly. Values closer to zero indicate optimal flatness. Digital models display readings numerically for enhanced clarity. For pointer models: First set the large needle to zero. When measuring, note the position of the small needle as the base reference. Subtract the base value from the final reading. Each full rotation of the large needle corresponds to 1mm (one division) on the small dial. For example, if the large needle points to 9, it represents 0.09mm; if it points to 90, it represents 0.9mm. The small dial indicates millimeters, with one division equal to 1mm. If the small needle moves two divisions and the large needle points to 43, the measurement is 2.43mm. Size: 30x4x1.1cm Material: Metal Color: Black Package Contents: 1 x Neck Curve Dial Meter Note: Light reflection and differences in display screens may cause slight variations in the color shown in images compared to the actual item. Measurement error allowance is +/- 1-3cm.