Measurements are the product. Width, projection, fixing height and the wall construction go straight to manufacture, and a transcription error produces something that cannot be returned or resold.
The diary follows the factory. Installation dates can only be promised once the manufacturing lead time is known, and a date given before that is a date that will be moved.
Installation is a two-person job with equipment. Access, scaffolding or a platform on a first-floor fitting has to be planned when the order is taken rather than discovered on the morning.
Repairs keep the winter busy. A recorded history of what was installed where, and when, turns the quiet months into servicing and recovering work on the company's own installations.