Hyundai HYBCF31 User Manual page 13

2.7. Grass trimmer assembly.
To fit the trimmer head you need to undo the retaining nut (clockwise direction), then remove
the retention cup and the clamp plate (Keep these safe they are not used with the trimmer
head).
Using one of the supplied 4mm Allen keys lock the shaft, then screw on the trimmer head in
anti-clockwise direction make sure head is fully tightened.
Remove the Allen key before use.
To remove head reverse the process.
Page 13 Ver 4 - September 2016