What is a "center block"? are there any other options where you are. For a low wall like that, you could use a segmental retaining wall block that does not require a footing or any mortar. It have an architectural colored split face and not a smooth face. - They are available in most countries and the U.S.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!