As a sole handicraft design, window construction (as a craft including measurements and installation) is only very rare. Over the last 30 years, the trend has been towards industrial production. The industry has split up into two fields: window production and assembly. The assembly company measures and constructs the windows with the necessary details, calculates the production and installation costs and offers that to the customer. After commissioning, he has the windows built during production. After delivery, he builds it and is also responsible for the entire building connection (grouting).
As a rule, there are 2 trades companies:
1. Window construction (usually only takes over production)
2. Installation (all other related activities)
It is even more serious in interior doors. There, the doors are bought and installed almost exclusively from the doors (warehousing and custom-made) or wholesalers (warehousing).
Thus, a coupling of production and installation is obsolete and no longer up-to-date. This is the situation in Europe, i do not know, how it is around the wold.