How to Hand Split Flagstone

Mark the line you wish the stone to break along using a piece of chalk or a pencil. You could also scratch the line in with the edge of your brick set. To get a tight fit with another piece in the pattern, lay the piece to be cut on top of that piece and use it as a template to show you where the line needs to go.

Place the blade of your brick set (which is a wide-bladed chisel) along the line you marked and strike the end of the handle with a mini sledge to cut a groove into the stone. Aim for a groove about 1/8 of an inch deep along the whole line you marked.

Lay down a piece of scrap lumber and set the stone you wish to split on top of it, with the area you want to split off hanging over the edge of the wood.

Lay another small piece of wood on top of the stone in the area you want to split off. This will catch the blow from the hammer and prevent it from chipping the stone, preserving the broken-off piece for future use.

Hit the small piece of stone once with a sledgehammer (for big pieces) or a mallet (from small ones). If you are hitting it with a sledge, you may need to ask someone to stand on the other end and weigh it down. On impact, the stone will snap along the line you scored into it with your brick set.