The line of small domed studs running around the edge of the back on this chair is set by hand, one stud at a time, and the spacing is decided before the first one goes in.
The trouble is that the border it follows is curved, and it has to end where it began. If the upholsterer simply starts at one corner and works round at a fixed spacing, the last few studs arrive at the finish line either crowded together or with an awkward gap - and that is exactly where the eye lands, because it is the point where the two ends meet.
So the length of the whole run is measured first, then divided into equal steps that come out whole. The spacing that results is rarely a round number, and it changes slightly from chair to chair because every chair is built to its own size. A marking gauge is set to that figure and walked round the border, marking each position before any stud is driven.
After that it is patience. Each stud is set with a soft-faced hammer, upright, seated to the same depth as its neighbours - because one stud sitting a fraction proud will catch light differently and stand out from the whole line. It is a long, quiet job whose entire purpose is to look effortless.