Layout the cut on the brick or stone's finished surface with a pencil, using a carpenter's square as a straightedge. Always cut brick and stone from the finished surface toward the back side.
Lay the brick or stone on a solid surface with the finished side facing up.
Press a bolster chisel's blade on the pencil mark. A bolster chisel has a wide and thin blade, usually 3-inches wide and about 1/8-inch thick. The blade centers below the bolster chisel's handle.
Create a 1/16- to 1/8-inch-deep mark along pencil line on the stone or brick's finished surface with the bolster chisel and a hammer. Strike the chisel's handle lightly several times until the line completely scores the brick or stone's surface. Pay special attention to a brick's corners.
Center the bolster chisel on the scored mark and strike the chisel's handle sharply. Continue to hit the chisel until the brick or stone snaps.
Trim the brick or stone's cut edge with a cold chisel and hammer, if needed. Hold the cold chisel's blade against the top of the rough cut and strike the chisel with the hammer. Repeat this until the cut edge has the desired finish. A cold chisel has an angled blade the same width as the handle.