The Jaras 4-in-1 Grand Regulating Rack is a tool that has been developed to take the guesswork out of grand piano regulation. This tool performs the regulating functions with precision. It is a quality made item which will last a lifetime and pay for itself many times over. The adjustments that can be made with this tool are: Grand Piano Let-Off, Check String Height, Backcheck Regulating Gauge and Damper Regulating Gauge. Comes with complete written instructions.