The traditional method of laying or setting tiles on the sheathing *noji 野地 of the roof. There are two basic types of tiles to be laid: the broad, concave tile *hiragawara 平瓦, and the semi-cylindrical convex tile *marugawara 丸瓦. The latter are also called cover tiles because they are set over the seams made by the continuous rows of hiragawara. The hiragawara are laid beginning with the eave edge *nokisaki 軒先. Problems arise because curves differ on various parts of the roof, for example the direction of the eave curvature at the eave ends of the roof and the curvature of the ridge itself. It requires the utmost skill to accomplish the transition between the two curvatures smoothly. The sheathing is curved in accordance with the underlying structure, so, the hiragawara must be evenly placed over the entire surface. If there is any tilt, the roof will leak. Special problems arise along the drooping verge *minokō 箕甲 and at the corners of the roof. Positioning the semi-circular convex tiles also requires tremendous skill. Seen directly from the front, the convex tiles usually appear in perfectly set lines from eave end to ridge. However, if the same roof is seen diagonally, looking toward the ridge, the concave tiles are visible, and the diagonal line of the tiles should also appear straight. The same is true of a roof covered with pantile *sangawara 桟瓦. The imaginary diagonal line is called karigane 雁足 (wild goose foot).