Please see below configuration of Non-Working Days in ClickHome3. All 4 fields are required in each row to be filled in for the system to take into account the date. This is to be managed by the builder under Administration>Company>Non Working Days screen.
Tasks can still be schedule on non-working days if manually scheduled by the supervisor of the job, nothing stops this from happening as working on weekends and public holidays is still possible.
Auto-scheduled tasks will take into account non-working days and won't schedule tasks on them - if the auto-schedule date falls on a non-working day then it will be scheduled for the next working day.