Recently while I was traveling in a foreign country (Italy if it matters), I had occasion to need to make the 1-1/2" knife blade on my pocket knife as sharp as possible -- ideally "scalpel sharp". It's night-time (about 10 pm local time) in an urban area and we're heading back to our lodging. There are no nearby open stores. [Note: there was an open pharmacy but it's just that -- they don't carry razor blades there].
I finally decided to use a stone, brick, concrete, or similar surface as a sharpening stone -- and I didn't have any facility for either flattening whatever I choose or even measuring flatness except by eye or feel. I finally found a small area on the corner of a stone building that felt smooth and flat enough and I used some available moisture to perform a honing operation until the blade felt smooth and sharp enough -- measured totally qualitatively by running it across the surface of my thumb-nail.
We went back to the lodging, boiled water which we used to "sterilize" the blade and performed our makeshift surgery fairly successfully -- the blade was, in fact, sharp enough that there was no pain when used to create a 1/2" long, ~1/8" deep incision into a section of calloused skin and the underlying healthy tissue.
Enough of the medical saga and onto the real question: Are there any suggestions for sharpening a blade under these conditions that would have been either easier or better than what I did?
TIA Norm