Most weed trimmers have removable heads so you can alternate between trimmer blades for heavy trimming and line heads for regular trimming. When you need to change over to the line trimmer you will need to remove the trimmer blades. Some trimmers use a blade without a head, but the disassembly process is similar. It is a good idea to keep the retaining nut and blade head together when storing the head.
Unplug your weed trimmer spark plug wire from the spark plug. If you have an electric weed trimmer, disconnect the power cord from the weed trimmer.
Locate a hole on the side of your trimmer spindle head. Some trimmers have the hole above the shroud. Insert the locking tool that came with the trimmer or a small Phillips-head screwdriver that will fit into the hole.
Rotate the trimmer blade head until the locking tool or screwdriver moves down and locks the gear hub. This will prevent the spindle from turning while you are removing the trimmer blade head.
Turn the cap on the bottom of the trimmer blade head counterclockwise. Remove the retaining nut and pull the trimmer blade assembly off the trimmer spindle shaft.