without being facetious with regards this question, if it was asked in the quite literal term, then simple common sense comes into play as to when and when not to wear the kilt, you have bear in mind that a majority of the kilts worn in the Highlands of Scotland on a daily basis will be 8 yard knife pleated hand stitched varieties that are either heirlooms passed down from faither to son, or substantial investments by the wearer, as such they are not subjected to the daily rigours of a manual working life.
I myself wear the kilt for work, my work is in a clean environment so the kilt comes to no harm, now if I was a sewage worker or diesel mechanic then no way would I wear the kilt for work.
Although as we have said the kilt is rarely seen as an everyday garment here, in some cases it is, and it's accepted without question on any occassion however badly or correctly it's worn.
Maybe if you could be more specific with the question, we could be of greater help.