Most walls require smaller bricks at their ends. Before cutting a brick, place it in a bed of sand or dirt to absorb the shock of the blow. Place the sharp end of a brick chisel at the line where you want to cut. Use a hammer to tap the end of the chisel, scoring lines on all four sides where the brick must be cut.
After scoring the lines, hold the chisel on one of them, slightly angled toward the side of the brick that will be kept and used on the wall. With your other hand, strike the handle of the chisel with a hammer. The blow should break the brick cleanly in two.