How to cut a brick wall opening
This is an important step that will make sure your bricks are laid level. Feed the string line behind the piece of wood that is clamped to the wall, at the level you want your first course of bricks to be. Pull the string to the other wall and clamp it off, making sure that it's tight and is level.
Lay a small bed of mortar for your first brick to lie on and use the spirit level to make sure it's level. Place a small amount of mortar on the top of the first brick and place another brick on top of it, at a downwards angle. Carefully pull the string line under this brick, this will give you the straight line you need to lay your first course of bricks. Lay a bed of mortar on the solid foundation for your wall. Apply mortar to the side of the bricks but feather it away from the sides. Lay the bricks next to each other in a straight line and use your spirit level to make sure it's flat.
To cut a brick to size, use the back end of your claw hammer. Mark where you want to cut the brick and with your safety glasses on, hold the brick in your hand and gently tap it with the hammer until a crack appears. When it does, hit it a little harder until the brick breaks.