Block retaining walls, when properly constructed, serve as practical, attractive and enduring landscape features. As part of the installation process, you will likely need to split some blocks to fit the length of the wall and stagger joints between rows. Even though splitting the blocks, as outlined, does not require power tools, it can still be dangerous. The major safety concern with this project involves the possibility that pieces of block will go flying when you are using the chisel and hammer, so always be aware of your surroundings. Wear protective gear that includes safety glasses, and ensure children and any other workers or observers are sufficiently away or shielded.
Draw a line around the entire block where you want the split, using a speed square and chalk or a pencil.
Score the block on all faces along the line by placing a masonry chisel on the score line and hitting it with a 1-pound hammer. Move the chisel along the line and turn the block over, as needed. Ensure the block is scored along the entire chalk line.
Place the chisel against the score line and tap the chisel with the hammer until the block splits.