What size wrench does Helen use to adjust the piano?

Helen's piano is tuned with a 1/4 inch wrench (that is, the wrench opening is 6.35mm). According to the query of Jiuzheng building materials network. Wrench is a necessary tool for Piano tuner to adjust the piano. They come in different sizes and shapes and can be used for different types of pianos. 1/4 inch wrench is the most commonly used wrench for piano tuning lawyers, and can be used to tune all strings of the piano. The length and shape of the wrench are designed to facilitate the tuning lawyer to tighten or loosen the piano strings.