There are three ways to check a guest in or out in Caterbook - from the Dashboard, the Calendar or from within the booking record itself.
From the Dashboard - click the door icon to the right of an entry in either of the Arrivals or Departures panels:
The status of the booking, and colour of the icon, will change to correspond with the legend on the Calendar:
From the Calendar - right click on the booking to 'Edit' it, then click either Check in or Check out:
From the booking record itself, go to the Rooms tab and click the door icon to the right of the room you want to check your guest in or out of:
Once checked in or out, bookings on the Calendar will change colour, from yellow (To Arrive), to blue (Checked In), and then grey (Checked Out):