Determining the correct measurements is especially important, when windows in an old building need to be replaced.
Existing blueprints can be very helpful, but the given data may not be up to date, requiring all dimensions to be re-measured.
If differing measurements are detected, you need to write them down and note the date of change.
This saves time for renovations at a later date and can help avoid problems during the installation.
In order to help you with this, you can print this document and use it for your notes.