Under normal use, you need to advance your string trimmer’s nylon cutting string whenever the tool isn’t cutting effectively. That happens every few minutes or even quicker in tall grass and weeds.

When I bought a home 25 years ago, for the first time, I needed to mow my own yard—an 80-square-foot, postage-stamp-size area. I got a hand-me-down corded string trimmer and started hacking away with ...