A lawn trimmer is a major component of any homeowner's yard equipment arsenal. Trimmers are either gasoline or electric powered and use a rapidly spinning plastic line to cut grass around objects that are difficult to reach with a lawnmower or other tool. They come in many types and sizes, some with extra functions such as concrete edgers or blades that are interchangeable with the line. Replacing the plastic line isn't difficult, but it does take patience.
Clean any debris or dirt that's around the trimmer's line spool. A clean spool will spin better and allow the line to advance without binding.
Verify that the new line is the proper size for the trimmer. That information is usually printed in the owner's manual and on the spool.
Remove the spool from the trimmer body. Some trimmers have small metal clips that hold the spool in place, while others have plastic retaining knobs. Use the flathead screwdriver to pry the spool free gently.
Open the spool, and remove any debris or old line remaining inside. Also check the spool for any damage.
Attach the end of the new reel of trimmer line to the spool through the anchor hole in the spool, which is usually clearly marked. Feed at least two inches of line through the anchor hole.
Wrap the line slowly around the device in the direction stamped on the spool. Stop wrapping line when the spool is about 3/4 full. Some models have an indicator mark that shows when the spool is full.
Measure about another six inches of trimmer line and cut it from the rest of the reel with the scissors or a utility knife. Feed the end through the line feed hole, from the inside of the spool out, and pull it tight.
Hold the spool and wound line tightly to minimise any unspooling and carefully place the spool into the trimmer housing. Be sure the feed line isn't trapped and feeds through the small hole in the spool housing.
Tug gently on the feed line to see if the spool shifts slightly from side-to-side in the housing. This shows it is attached properly.
Line sizes are usually colour-coded and clearly marked on the package. Use WD-40 or cooking spray to coat the spooled line and avoid any binding before replacing the spool.
Don't use old, crimped line or line that has begun to stick together. Be sure the trimmer will not accidentally start while replacing the line.