CENTERING, a term applied to the erection of temporary woodwork to support arches, etc., while they are setting. Thus, in the case of an arch, the carpenter forms a "turning-piece" shaped to take the bricks or masonry, and properly tied and braced. This is strutted in position, when the arch is completed by the bricklayer or mason. As soon as the work is set, the centering is carefully removed, which is called "striking the center ing." The same method is used in building brick sewers. The origin of the word "centering" is obvious from the primary use in centred arches, but the same term is applied to the use of scaffold-boards to support concrete floors while they are setting hard. (See CARPENTRY.)