Abstract: A cement block mold which includes a base, a top cap and a flexible sidewall strip. The base has an upstanding peripheral sidewall with a single slotted engagement. The top cap has a downwardly extending peripheral sidewall with a single slotted engagement. The flexible sidewall strip having a first engagement at a first end and a second engagement at a second end. The sidewall strip is secured in position by bending the sidewall strip to form one of a circle or an oval, and then engaging the first engagement and the second engagement with the slotted engagement of the base, and then engaging the first engagement and the second engagement with the slotted engagement of the top cap.