The best material for metal conductors is copper, but galvanized iron and tin are used to some extent.

The usual form of a copper gutter is shown in Fig. 158, but it is often necessary that the face should he formed of mouldings to match or form part of a stone or wooden cornice. In this case, the gutter is formed behind the finished moulding. (Fig. 159.) The gutter shown in Fig. 158 is made of sheet copper, turned over an iron bar A, and moulded to form the trough, and made wide enough to run well up on the roof boarding, under the slates or other roof covering. Bars of copper or galvanized iron are bolted to the outer bar, and nailed and soldered to the roof. These bars should be given a short twist, as shown, so that the wash of the roof will drip off into the gutter, and not follow the strap down and soil the face of the gutter. In the case of the lined gutter, Fig. 159, the outer edge of the metal is tacked to the wood or tucked under an iron bar previously secured.

Standing gutters (Fig. 160) are sometimes used where they will not be objectionable by reason of holding back the snow, but are often a source of trouble.

In a great many cases of city building, especially with flat roofs, iris necessary or convenient that the outer walls shall be carried up as a parapet, and the roof water taken care of inside of the building. In this case a "cant-board" is used, shown in Fig. 161. This consists of a board surface set in the angle of roof and wall, and graded to the desired outlets where conductors are placed inside of the wall.