Use checkboxes to search for records with a given characteristic. If only records with this characteristic are to be searched for, the state of the box  is selected, if exactly these records are not to be searched for, the state  is not selected. If the state  is undefined, then both data records with and without the characteristic are searched for. Examples with module series and multi-day events^M

1. By default, checkboxes are usually  undefined. The values of the field are not taken into account for the search.
   Bsp.:  Mehrtagesveranstaltung findet sowohl Eintages- als auch Mehrtagesveranstaltungen.
2. If the box is selected with a single left click  , only records that have the selected property are searched.
   Example:  Multi-day event only organises multi-day events.
3. If the box is not selected by left-clicking again  , then records with the selected property are excluded from the search results.
   Bsp.:  Mehrtagesveranstaltung findet keine Mehrtagesveranstaltungen.
4. With a third left click you restore the status  undefined .