Figure 237.—Technique of carved slabs, Mangaia. a, cross section of rectangular slab; shaded sections regularly spaced are parts to be removed. b, cross section through lozenge holes; with shaded parts in a removed, slab divided into four ridges (1) in front and back and two (2) at ends; shaded portions show sections through middle of fore-and-aft lozenge holes (3) and end holes (4) between two end ridges which run into adjacent fore-and-aft holes; ridges average about 22 mm. in width. c, upright view: showing longitudinal ridges (1) and end ridges (2); ridges are square-cut and of even thickness. d, notches (1) cut in ridges and so spaced as to leave alternating smaller (2) and larger (3) rectangular spaces on outer surface of ridges; smaller segments formed solid pillars while larger sections were perforated (4) from side to side to form arches (5); notches on all ridges cut on same level so as to form horizontal series of pillars and arches as well as vertical sets; lozenge-shaped holes (6) between ridges obscured by angle of drawing, but top section through holes shows three fore-and-aft holes and end holes as in b.