Hi I'm Mark Sullivan for Expert Village and today we're going to learn how to build a barbecue pit. So you can feel these grooves in the bottoms of the brick locking in to the bosses or the pegs, which are sticking up out of the brick beneath it. So these grooves fit onto these little bumps, these bosses, these pegs that are cast in to the bricks. They lock in that so that this will hold in place for many years without additional maintenance. I'm going to continue moving these around. We're going to set this row in place, and then we'll come back and revisit all of them and see which ones we want to move out of place, or replace and then which ones are suitable for our second course of hexagonal blocks.