Abstract: A control joint device including a reciprocating means, a surface breaking member and a ridge member having a generally flat bottom surface except for a first ridge along, at least, a portion of its length, wherein, in use, the first ridge of the ridge member is positioned behind the surface breaking member, the surface breaking member is mechanically reciprocatable in a straight line between a first position and a second position along an axis substantially perpendicular to the plane of a setting material, the first position being substantially level with the first ridge of the ridge member and the second position being spaced apart from the first position and wherein the ridge member further includes a planar surface from which the first ridge extends.