In a pinch the unfinished rim on the bottom of a ceramic coffee cup will give a good edge. That's all my grandmother ever used on her kitchen knives and they were sharp.
poppy65, when I worked at the processing plant, I preferred a ceramic "steel" (edge hone)!!! Some people liked a grooved steel while others like the standard, smooth edge honing steels.
Once you learn the art of using a steel, you can use, and I have, any hard, smooth, rounded metal...I like annoying my wife by using stainless steel and chrome plated wires on shopping carts (buggies?) at our local grocery store.
440 stainless will keep a modestly sharp edge, where high carbon can be truly sharpened without specialized tools. Problem with high carbon, the fine edge oxidizes fast and literally disappears.
Once sharpened, it is rare for the actual edge of lower carbon and stainless blades to dull when used properly...the edge rolls over so you wind up cutting on a rounded surface...that is what a steel is correcting..it straightens out the edge, it is not sharpening as there is no metal removed from the blade (a ceramic "steel" will remove fine oxidation).
Knives with higher angles may be sharper, but the edge is more of an ultra fine wire that is far more fragile, and needs corrected (steel honed) much more often...it's a personal preference finding the right mix of precision and durability on an edge...there is no right way or wrong way.
In processing, we preferred the ultra sharp high angle edge as we honed every other cut and our knives were replaced daily...or more if nicked. The fine, polished edges could cut nearly frozen back fat of a hog with little effort, pulling the curved specialty knife through in a long, smooth pull...no turning or sawing at all.