An edger blade is designed to spin perpendicular to the ground, with maybe a 5 to 10 degree tilt. It cuts grass and a bit of soil. That's the job.

Here's what most people do instead. They hold the edger at 30 or 40 degrees, dragging the blade through the gap between lawn and concrete, half-cutting half-grinding. The blade hits the concrete edge over and over. Each strike chips a tiny bit off the blade, dulls it, eventually breaks the tip clean off. We see blades come in that look like they've been run over with a chisel.

Here's how to actually use one:

• Walk in a straight line, edger held vertically. Wheels on the concrete or paving, blade just over the lawn side.
• Let the blade do the work. Don't push down on it. Let gravity hold the depth.
• Walk slow. Maybe half walking pace. The blade needs time to cut, not just smash.
• If you hit a tough spot, back up and go again rather than forcing through.
• Edge regularly. Every 2 to 3 weeks. If you only edge twice a year you're fighting a wall of overgrowth and that's where blades get destroyed.

Also, depth. Most edgers have a depth adjustment, usually a wing nut or a lever near the wheels. Set it so the blade goes about 25mm into the gap, no more. Deeper than that and you're cutting roots and rocks for no good reason.

Get the angle and the technique right and a decent blade will last 2 or 3 seasons. Get it wrong and you'll be buying a new one every spring. Blades are 15 to 40 bucks depending on brand. Adds up.