The art of dry stone walling requires knowing the tolerance level of the stones you are using.
If you impose a 'zero level' of tolerance on a stone material you create an uninteresting wall.
Stones offer us a lot of opportunity to put them in the wall in interesting ways, not just structural ways, and not always exactly "by the book". Stones are individuals and they are fundamentally very tolerant. If you refuse to work with their tolerances, or insist on minimizing them, you are not doing the stone or your wall any favours. You will have a minimally interesting wall and while you might impress your colleagues with your abilities to make the stonework look like block work, there is really no need to do so.
The trick is knowing and maintaining tolerances and working with the idiosyncrasies of the stones rather than trying to be in control all the time and shaping the daylights out them.
Andy Goldsworthy said that complete control can be the death of a work.
