The string on a string trimmer is the part of the machine that does the actually cutting of the grass. Sometimes the string becomes loose or needs to be replaced. It's important to rewind or wind a string trimmer correctly to prevent injury and make sure the machine continues to work properly.
Step 1 - Read the Manufacturer's Manual
Find out the specs of the string trimmer by reading the owner's manual. If you've misplaced the manual, you can usually find the information you need on the manufacturer's website. The owner manual will tell you what type of string the trimmer needs. It will also let you know if the trimmer is a double string or single string model if you don't already know. Buy the right amount of replacement string.
Step 2 - Open the Spool Retainer
Turn off the unit and unplug it from the power source if it's electric. Disconnect a gas string trimmer. Remove any grass or other debris from the housing of the spool retainer. Sometimes grass build-up can be heavy, and removing it allows you to more clearly see what you're doing. Firmly hold the string head with one hand and turn the spool retainer with the other in a counterclockwise direction. It'll be easier if you use your dominant hand to do the turning.
Step 3 - Remove the Old String
There may be a build-up of grass in the housing and around the string. Wipe it away so you can see what you're doing. Carefully take the old string off of the spool. Depending on the model, you can take the entire spool out of the retainer and then remove the old string. Other models will have the spool attached to the trimmer, meaning you'll need to pull the string out of the spool as it remains in the retainer.
Step 4 - Cut the New String
Use a pair of sharp scissors to cut a piece of string 9 feet long. If your manual says you have a double string model, then you'll need to cut two pieces. Make sure you use the sharpest scissors possible. Dull scissors will fray the edges of the string, making it harder to insert back into the retainer and wind smoothly
Step 5 - Wind the New String
With a steady hand, carefully insert one end of the string into the anchor hole of the spool. This may take a few tries since the hole is small. Once in, wind the string counterclockwise around the spool until you've used up all the cut string. Leave about 6 inches free at the end to put into the small slot located on the spool flange.
Step 6 - Wind Again for Double String Models
Repeat the same actions described in Step 5 around the bottom of the spool.
Step 7 - Replace the Parts
Put the spool back in the retainer if you've pulled it out completely. Reconnect the power source to continue working or store the string trimmer.