I just bought a house with a large retaining wall built out of stackable concrete blocks. At one intersection there's an extra block that sticks out awkwardly. If I score a line with a chisel can I get the block to cleave cleanly along that line? Or is the only way to use some kind of cutoff wheel or wet saw?
Yes that is the way to do it without a cutoff blade, it is old school. But you must chisel in deep enough, completely around the block that is accessible, before you strike with hard blows to break it on the score line you made. I have done this with as little as an 1/8" deep score, although deeper is better for a more sure result. Go around the block in levels. Light score all around, a little deeper the next pass. And so on... If you go too aggressive too quickly, it will not break on your desired score line.