Look, that tape is a ticking time bomb. It'll shift, melt from rim heat, or just plain fail when you hit a bump hard. A real rim strip costs like two bucks and takes two minutes to install. Using anything else is just asking for a sudden flat, or worse, a blown tire.

That 120 gsm cover stock is a good example. The bone folder works because it compresses the paper fibers along the grain instead of cutting them. A metal tool, especially if it's sharp, can actually weaken that fold line by severing those long fibers. It's not about being gentle, it's about working with the material's structure. Your friend is right that it gives a more durable fold for book covers.

Ouch, @lucashenderson, that's a painful truth right there.