This part of IS0 10545 specifies methods for determining the dimensional characteristics (length, width, thickness, straightness of sides, rectangularity, surface flatness) and the surface quality of ceramic tiles. Tiles with areas less than 4 cm2 are excluded from measurements of length, width, straightness of sides, rectangularity and surface flatness. Spacer lugs and glaze blobs and other irregularities of the sides shall be ignored when measuring length, width, straightness of sides, rectangularity, if these are subsequently hidden in the joints after fixing (installation).