Unplug the electric trimmer from its power source. If your trimmer is gas powered, remove the gas cap, flip it upside down, and drain the gas into a gas can. Place the gas cap back on once drained. This will prevent the trimmer from accidentally turning on while you are working with the trimmer head.
Pull on the large tap button located on the bottom of the trimmer head to remove the string spool. The trimmer head fits onto the trimmer shaft.
Remove the spring from the trimmer shaft. The spring is located between the trimmer-head housing and the spool. It may fall out when you remove the spool.
Locate the bolt on the side of the trimmer-head housing. According to customer service, you must remove the bolt with a wrench or socket and then slide the trimmer-head housing off the shaft.