| Often the gap between stones is filled with natural or a polymerized sand. The sand is dumped onto the surface and swept around to fill the gaps. In the case of the polymerized sand, once the gaps are filled and all excess sand is removed, the surface is carefully sprayed with water to harden the sand. This is more common when installing pavers with a more uniform gap. |
Here is a link that might be useful: Flagstone Patio Installation