The design concept of the roller tool: it is mainly used for repairing musical instruments such as piano players, musical instrument lovers, orchestras, and personal studios. The introduction of professional maintenance personnel proves that this tool is relatively practical, and focuses on solving depressions caused by accidents such as collision, dropping, and squeezing of some musical instruments, which can improve the appearance smoothness of musical instruments. Product introduction: There are quite a few kinds of tools on the market for repairing concave musical instruments. This tool enables our research and development team to re-integrate the use characteristics, performance and practicability of some maintenance tools after communicating with many professional musical instrument maintenance units in China, thus effectively improving the defects of the existing concave tools on the market. Our product is easy to use, easy to operate and suitable for most people. Features and advantages: 1. We have made this tool into a detachable assembly style for easy storage. 2. The roller in the middle can be changed in time according to the problems existing in different positions of the musical instrument. (For example, if some depressions are large and deep in area, it is necessary to use rollers with large angles first, then proceed step by step, and finally reach the initial state).