I've never tried it, but if I needed to turn a plain edge knife into a seatbelt slicer I'd take a sharp knife and give it a toothy edge on coarse stone. From what I've seen, a polished edge slides on nylon webbing rather than biting in. A coarse toothy edge should allow it to bite in. Never tried it, that's why I bought the Spyderco Rescue. An Endura with a 50/50 blade should do a fine job and would be a good general purpose blade. OTOH, I EDC only plain edge knives. The serrated knife I have is in the truck console.