When reloading line on a weed trimmer spool, be sure to use the correct type of nylon line. There are specific thicknesses for each type of weed trimmer, and the thickness will always be marked on the spool. It is important to use the correct thickness of line for the trimmer to operate correctly.
Remove the spool from the weed trimmer hub. Most have either side tabs that need to be pushed in or a central plastic nut that must be unscrewed.
Every spool has the correct line size printed on it. Common types are 0.80 and 0.95. Get the one that is made for your spool.
Inside the spool will be a little anchor hole for the line. Insert the new line inside.
Most spools wind counterclockwise. On the spool there will be arrows showing which way the line needs to be wound. Follow the arrows and wind the line.
Continue winding the line until the spool is almost full.
Use shears to clip the line. Hold the clipped end or the spool will unravel.
Place the spool back into the weed trimmer hub, and thread the clipped end through the exit port hole in the hub. Allow about 6 to 8 inches of line to extend from the exit port. Press the spool back into the hub and secure it with either the push tabs or the plastic nut.