US Patent 7748189 Tile and tack therefor

A tile having a self-interlocking mechanism urges rain water running on the surface of the tile to run downward thus making it for rain water to leak less through a joint. The tile includes a tile base, an underlap portion on each of an upper side area and one of a left-hand side area and a right-hand side area of the tile base, and an overlap portion on each of a lower side area and the other of the left-hand side area and the right-hand side area of the tile base. The tile may be arranged horizontally and vertically in a plain in a self-interlocking manner. The tile includes a tilt portion tapered thinner toward the lower end of the tile base.