Abstract: An assembly and method for extending the length of the output shaft of a string trimmer having a threaded output shaft spindle attached to a threaded spindle receiver of a mowing head is disclosed. The assembly and method includes providing a plurality of threadedly attachable shaft extensions preferably of different lengths, detaching the output shaft spindle from the threaded spindle receiver of the mowing head. Selecting a desired shaft extension from the plurality of shaft extensions and threadedly connecting the selected shaft extension to the threaded output shaft spindle and threaded spindle receiver of the mowing head. One or more shaft extensions may be connected together to create a shaft extender positioned between the output shaft spindle and the mowing head of the string trimmer.