71. Sheet-metal crestings are of varied design and construction. They can, in fact, be made in any design which is adapted to stone or terra cotta.

The most important features to consider in crestings are the method of support and the connection to a slate or shingle roof. Ordinary crestings are so constructed that the nail heads in the top course of slates are exposed to the weather. This is a mistake, as the rain will certainly follow the nails and cause slight leakage, which may not be visible, but which, nevertheless, hastens the decay of the timber and rusts the nails.