Edging a lawn with a string trimmer is done by flipping the head 180° so the shield faces your body, then guiding the tip of the line vertically along the pavement to cut a clean 2-inch-deep groove.
That walkway overgrowth is the same tool you just used to trim the rest of the lawn—you just have to change how you hold it. The trick is a 90-degree head rotation and moving opposite the line’s spin direction. This method saves you the cost of a dedicated edger and the shed space it takes up. Here is the exact setup and technique for a crisp edge every time.
Why Your String Trimmer Can Double As An Edger
Most straight-shaft string trimmers let you rotate the cutting head a full 180°, switching the line from a horizontal plane (for trimming grass) to a vertical plane (for cutting edges). The same motor and line that clears under a fence now carves a clean groove between your lawn and the driveway. This works on corded, battery, and gas trimmers alike—as long as the head can orient vertically or you can twist the whole unit.
Square, bump-head line handles the heavier cutting an edge demands better than rounded or twisted line, per Lawn Starter’s detailed guide on the technique. The tools that make this easiest are straight-shaft, loop-handle trimmers with smaller guards—model examples include the STIHL FS 56. Curved shafts and bicycle-handle units reduce precision for this move but can still work with practice.
How To Set Up Your Trimmer For Edging
Flip the trimmer head to a vertical position with the debris shield pointed straight toward your body. If your model lacks a rotating mechanism, simply twist the entire unit 90° in your hands to get the same angled orientation.
Now reposition your grip. Hold the shaft sideways so the top of it faces your body and your thumb rests on the trigger. This thumb-on-trigger stance gives you better control than a palm grip when the tool is inverted. Keep your arms straight and guide the tip of the line against the pavement edge.
Step-By-Step Edging With A String Trimmer
- Prepare the path. Clear away rocks, hoses, toys, and any debris that could become a projectile. Mow the lawn first so the grass is a uniform height.
- Check the line. Ensure the string is 4–6 inches on each end, long enough to reach the ground cleanly. Replace any line that is frayed, brittle, or shortened from use.
- Rotate the head. Lock it into a vertical (90°) position with the shield toward you. For fixed-head models, rotate the entire unit manually.
- Find your stance. Stand upright with the shaft held sideways. Grip the side of the shaft, not the top, and rest your thumb on the trigger.
- Set the angle. Hold the trimmer head perfectly perpendicular to the ground—any tilt cuts a messy gouge instead of a clean line.
- Start the motor at full speed before the string touches anything. Graze the grass-pavement interface using only the tip of the line to cut about 2 inches deep.
- Move opposite the spin direction. If the line spins clockwise, edge from left to right (debris flies into the lawn). For counterclockwise, move right to left.
- Take small bites. Work in short, controlled sections. Trying to edge a long stretch in one pass leads to uneven depth and a wavy line.
What Happens When You Move The Wrong Direction
Traveling with the spin direction blasts clippings and dirt across the sidewalk or driveway. The debris ends up on the hard surface instead of the lawn, which means extra sweeping. More importantly, it makes it harder to keep the line tip against the pavement for a consistent cut. Moving opposite the spin keeps the debris inside the grass line and lets the string carve the edge cleanly.
If you find yourself fighting to keep a straight line, stop and confirm you are moving against the rotation, not with it.
Common Mistakes That Ruin The Edge
- Canted head. Tilting the trimmer instead of keeping it vertical cuts a ragged trench. Check your angle every few passes.
- Looking at the head. Staring down at the trimmer makes you walk crooked. Keep your eyes on the path ahead and let peripheral vision track the line.
- Pushing too deep. Forcing the string more than 2 inches into the soil digs a messy rut instead of a defined groove.
- Edging wet soil. Soft earth after heavy rain turns the cut into a muddy trench. Wait at least one day after rain for firm ground.
- Cutting concrete. Letting the line ride directly on the sidewalk frays the string fast and dulls the cut. Graze against the grass, not the pavement.
The Best Trimmers For This Technique: A Quick Look
| Trimmer Type | Why It Works For Edging | Precision Level |
|---|---|---|
| Straight-shaft, loop handle | Easier to invert and control; smaller guards allow vertical head placement | High |
| Straight-shaft, bicycle handle | Still usable but requires more wrist rotation; thumbs on triggers help | Medium |
| Curved-shaft, any handle | Difficult to maintain vertical angle; limited control for precision edging | Low |
| Battery (cordless) models | Lightweight and quiet; constant torque helps with vertical edging | High (if straight-shaft) |
| Gas models (e.g., STIHL FS 56) | Powerful and balanced; straight shaft and loop handle ideal for technique | High |
| Corded electric models | Works if head rotates; cord can limit reach and get in the way | Medium |
| Multi-head trimmers (with edger attachment) | Dedicated edger head makes this unnecessary, but can still trim-and-edge | High |
When The Technique Still Feels Awkward
If the upside-down grip hurts your wrist or the line keeps breaking, check two things. First, make sure you are using adequate line length—4 to 6 inches per side is the sweet spot. A worn line fractures easily and kills the cut. Second, confirm your trimmer’s head is locked at a true 90-degree angle. A loose pivot means the line wobbles, which introduces that rocking motion that throws off the edge.
For anyone ready to pick a dedicated tool that makes this easy, we tested the top models side by side. Our string trimmer for edging roundup covers the best straight-shaft options for precision edge work.
Edging Depth And Line Selection
| Grass Type | Ideal Edge Depth | Recommended Line Profile |
|---|---|---|
| Bermuda | 1.5–2 inches | Square (bump head) line |
| Fescue | 2–2.5 inches | Square or star-shaped line |
| Zoysia | 2 inches | Square line |
| Kentucky Bluegrass | 2 inches | Square line |
| St. Augustine | 2–2.5 inches | Square or multi-lobed line |
| Overgrown edges | 2.5–3 inches (first pass) | Thicker square line (0.095–0.105 inch) |
Edge Line Checklist: Final Cuts
- Clear path of debris before starting
- Mow lawn first for uniform grass height
- Inspect line—replace if worn or short
- Lock head at 90° with shield toward you
- Grip shaft sideways, thumb on trigger
- Start motor at full speed before touching ground
- Graze tip of line at pavement edge, 2 inches deep
- Move opposite the spin direction
- Work in short sections, keep eyes ahead
- Wait for dry soil before edging after rain
- Wear eye protection against flung debris
FAQs
Can any string trimmer edge a lawn?
Most straight-shaft models can handle edging when the head is rotated vertical. Curved shafts and bicycle-handle units are harder to control and deliver less precision, but they can still work if you twist the entire tool 90° and hold it sideways.
How deep should the edge cut be?
Aim for about 2 inches deep. Going deeper creates a messy trench that collects debris, while a shallower cut disappears after a few mowings. The 2-inch depth establishes a visible boundary that lasts until the next trim cycle.
Does edging damage the string trimmer line?
It wears the line faster than regular trimming because the tip scrapes against soil and pavement. Using square, bump-head line reduces fraying. If the line breaks often, you are probably pushing too deep or riding directly on concrete.
Should I edge before or after mowing?
Edge after mowing. Trimming the grass first sets a uniform height, so the vertical edge cut is consistent along the whole border. Mowing after edging tends to scatter the freshly cut clippings back onto the walkway.
What direction should I walk when edging?
Move opposite the direction the line spins. For clockwise-spinning trimmers, walk left to right so debris is thrown onto the lawn instead of the hard surface. This keeps the cut clean and minimizes walkway cleanup.
References & Sources
- Lawn Starter. “How to Edge Lawn with a String Trimmer.” Detailed steps on head rotation, walking direction, and cutting depth.
- Your Green Pal. “How to Edge Your Lawn Like a Pro.” Covers grip technique and small-bite approach.
- Friday Parts. “How to Edge With a String Trimmer.” Line length, shield positioning, and direction rules.
- Home Depot. “How to Edge a Lawn.” Safety tips, path clearance, and wet soil warnings.
- Scotts Miracle-Gro. “How to Edge a Lawn.” General technique and cleanup guidance.