There are many reasons as to why you may need to block your calendar.
These could include, you are using the vehicle yourself, the vehicle is damaged or you are away from home and will not be able to handover the vehicle. For whatever reason you need to block your calendar, it is a good idea to do so. This lets Travellers know when your campervan will and will not be available.
To do so you need to click on your username in the top righthand corner, select "My Motorhome(s)", choose the vehicle and select Availability. Once on the Availablity page you will be able to select the button "Add Blocked Period" and choose the period you would like to block your calendar for.
Make sure you click the blue 'Save' button on the listing before leaving the page to save your changes.