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(Illustrated on Plate 3)

   Small sheets, with ½-inch seams, flat-locked and soldered, are used for flat roofs (less than (1 on 3) and decks. The size of sheet which best combines economy and practicability, is about 18 by 24 inches.

   The sheets are tinned on all sides and are then formed as

required to make ½-inch locks with adjacent sheets. Each sheet is held in place by copper cleats and the seams are then malleted down and soldered. (Fig. 1.)

   As no nails are driven through the sheets, they are free to move and all stress from expansion is taken up by the cleats. This stress is scarcely appreciable in any one cleat, and, as the cleats are uniformly distributed over the roof, expansion is amply provided for.

   If there is no likelihood of water collecting on the roof, because of clogged outlets, white lead, instead of solder, can be used for closing the seams.

   All flat enclosed roof surfaces, such as balcony decks, should be built with scuppers in the enclosing walls so that water will not back up and freeze in the winter when the outlet is obstructed.

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