Ten years on, the difference between two coaches that left the same shed usually comes down to one stage nobody photographs.
Ask an operator what makes a body last and most will say the paint, or the panels. It is neither. It is whether the skeleton was square when the first panel went onto it.
A frame that is a few millimetres out will take the panels anyway. It will look fine at handover. But every joint is then carrying a load it was not drawn to carry, and over a few thousand kilometres of Rajasthan highway those joints start to work against each other. That is the rattle that appears in year three and never goes away.
So the skeleton is jigged and checked before anything is skinned. It is the least visible stage of the build and the one that decides the other nine years.