How do I make a service technician unavailable?

In order to make a technician "Unavailable," you must first enter into the Powerboard located inside of your toolbox. Once here, locate the "Unavailable" tag above your unscheduled tickets:

Drag and drop the unavailable tag to a technician's date slot that he is unavailable for.

Keep it mind, you can always change the "Unavailable" text by clicking on the tag and pressing the "Edit" button.