The ability to block reservations on the fly is very important for restaurant owners that are constantly dealing with operational changes or get fully booked on the regular.
To block restaurant hours on the fly, From the Table Manager, click on the 
dropdown on the top right and choose "Blocking hours".
You can now block hours for the current day you are viewing.
Start Block Time: The time you want to start the block
End Block Time: The time you want to end the block
Online vs. In House: You can also choose to block only online or only in-house or all reservations.
You can also edit or add blocked hours by going to Availability > Block Hours > and clicking Block new hours
From here you may now edit existing blocked hours or block new hours.