For guitars without adjustable truss rods (many/most Classical guitars, for example), heat treating the neck is a viable way to rectify neck relief problems. In other cases, where the truss rod is no longer effective in adjusting out excessive relief, heat treatment can help in restoring function to the truss rod. Gentle heat is applied while the neck is pulled back into the desired relief. The neck is then allowed to cool naturally and remain clamped in position for 12-36