Everything is edible, but only some things are edible multiple times.

I think everyone should learn how to sharpen a kitchen knife at least.

Dull knives are dangerous, and it really only takes an afternoon to get decent at sharpening a knife.

Unfortunately there’s a lot of lore about knife sharpening, like how you need really fine grit stones, or a whetstone being the best, when in reality you can get a shaving sharp edge from a 20 dollar diamond stone from a hardware store. Sure, a 4000 grit stone will get you a mirror finish and a more refined edge that will last slightly longer, but even an 80 grit stone when used properly, will get you a good edge that will last for months without any other sharpening.

It’s a single bevel.

Sharpen the angled side at the proper angle, and remove the burr by flattening the smooth side of the blade on a decent diamond stone.

I have my great grandfathers barber’s shears, and that’s how they’ve been sharpened for going on 100 years now. You need a stone wide enough for the whole blade, so that its uniformly flat, but other than that it’s pretty logical how they need to be sharpened.

That extends to all tools in my opinion.

Don’t borrow someone’s tools without their express permission, and don’t lend someone a tool unless you either know what they’re doing with it or you don’t care if it gets damaged.