A flange, or raised rim, of dovetailed or under-cut section is formed on the top half of the uppermost side of each tile (see Figs. 79, 80), and on the lower half of the undermost side (the latter is dotted in Fig. 78). The upper flanges correspond to r r. Of course B in the figure hooks on to the lower flanges s s. This holds them firm, and it is said to exclude wind and rain and to render pointing unnecessary.
The various lengths may be joined by pegs, holes for which are left in the rolls, as in Fig. 71, or they may be made to lap, as in Fig. 82.
In some varieties fleurs or other ornaments are made in one piece with the tile.
Other kinds, such for example as the Broomhall tiles above mentioned, require special ridges.
Hip and Valley Tiles are made of special shapes, to fit the hips and valleys of tiled roofs. Their form necessarily varies according to the pattern of tile and the pitch of the roof to which they are to be fitted.