To provide a tool designed to adjust the length of a string and facilitate its correction without stretching the string again through eliminating such a problem that, in fixing branches by stretching them with a string in order to make the shape of the branches of a tree better, the string may become loose with the lapse of days, in this case, the string is stretched again for correction, thereby requiring time.

The tool has the following structure: Guides(2) are provided on both sides of a shaft(1) and furnished with notches A(3) and B(4). This tool is set up at an intermediate point of a string being in stretching branches to adjust the length of the string. Thereby, the string can be corrected by adjusting the length of the string without stretching the string again.