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