Our teachers have substitution duty lessons, we need min 2 at each period

!!!ATTENTION!!!
Use this solution only in case, you are not using ASC Substitution online feature, which we strongly recommend to you - see this topic: What is aSc Substitution software good for?

1. Define new subject "Substitution Duty"
2. Create a lessons 'Without class' with this subject.
3. Then add this card relationship:

You can mark some periods in the timeoff map. The software will then ensure min 2 substitution duties on these marked periods only.

On other periods there may be just one, or none. On the marked periods there will be 2 or more.

Note:
In some schools this solution is not applicable because it requires you to define how many times each teacher shall have substitution duty.
If you do not know this in advance, you can use this solution:
We need two free teachers on each period to make sure we have enough teachers for substitutions