I don't know we always make reservations.
I would definitely make reservations to dine inside. Or you can pick up food at the to go window and eat it at the patio. The wait to do that is normally 5-10 minutes. However long it takes them to pack your food. Very nice outdoor seating area.
I am not sure but I would reccomend that you reserve a table by Googling Killen's Barbecue. I checked a moment ago and I saw 6pm being the closest time to 5pm on Saturday. Hope this helps.
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