We have recently introduced new functionality as part of Appointments release 3.2 which allows the restricting of appointment slots by hours, age and sex so that appointments can be booked appropriately.
These restrictions are only applicable for staff using Appointments within practices or shared care settings, but do not currently apply to slots being booked outside of your organisation, for example, by your patients online.
This issue is due to be fixed shortly, in the meantime we strongly advise you not to use restricted slots for appointments that can be booked outside of your organisation.
For more information on how slot type restrictions can be set, and other new features of Appointments release 3.2, see the release guide here.
