Slap it on a grinder - Sacrilege!!!

[Glug]

I've sharpened knives on rocks along lake shores in the past.

I had the realization a few years back that the bottom of a coffee cup works pretty well. It's handy if you are cooking where the knives are dull. Though it won't correct abuse or remove much material.

Bonus - if your pocket knife needs a touch up, it will give you something to do while waiting at the coffee shop for a friend. Double bonus - no one is likely to bother you.

I stray from the topic but a Lansky sharpener works well for small knives and allows the angle to be exactly set. It also allows multiple angles for relief. It is a bit more challenging on longer blades.