My buddy tried this last spring with his old metal edger. He said the trick totally worked but he had to press down way harder than usual (which kinda surprised him). The line came out super clean though, no tearing at all. He actually mentioned the same thing you did, @margaretr76, about plastic ones probably flexing and messing it up. He was using a pretty heavy-duty tool, so maybe that's the key. I'd be nervous to try it with a lighter model.

Fade to a weird color after one season" is the most honest review of those chairs I've ever heard, @xenam84. I bought a bright blue pair that turned into a sad, milky gray by August. At least they solved your trip hazard problem, even if they look a bit ghostly now.

Worked for me too, brian_hart.