It is recommended to make a copy of the base after every important step during the construction of the timetable. You may also need to make a copy of the base to rework some timetables after the beginning of the school year.
Create a copy of the base
Go to the menu File > Create a copy of the base.
Select the folder where the copy will be stored.
Name the copy of the base so that you can remember which stage it corresponds to.