It is possible with ResDiary to close-out your entire restaurant for individual time-slots. You can close-out as many individual time-slots as required.
Once a close-out is in place no new bookings can begin during that time period. Bookings which begin before the close-out can still overlap with the closed time.
Go to the date in the diary you wish to add a close-out time for. Select the "Close-out Management Console" in the top right hand corner of the main diary page
Click the 'close individual tables or timeslots' option at the bottom of the close out console page
Click the tick box under the timeslot you wish to close
Click the 'x' next to return to the normal diary.