You can block availability manually in the system through the Master Calendar. To do so, go to Frontdesk - Master Calendar. Below the Calendar grid, select "mark product as unavailable".
This will open the Change Availability page where you can add a manual block to the product. Select your product (or All), select unit (if applicable), enter dates of block (enter time for hourly/schedules, if needed), and comments. Once completed, click Save.
After you return to the Master Calendar, you can see the block you added as indicated in gray on the calendar.
Note: Manual blocks to products made in the Master Calendar will be indicated as 'Sold Out' (in red) when viewed by the customer via the online booking calendar. As well, any comments added will not be shown to the customer, and only seen via the backoffice on the Master Calendar.