This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
Generally these shingles are laid from the eaves up to the ridge. There is, however, a method of laying the shingles from the ridge downwards. In laying shingles of the Gothic pattern (one of which is shown in Fig. 52), the gutter and eaves flashing should be set as shown at a, Fig. 53, the flashings being carried up about 6 or 8 inches on the roof boards. A start should be made at the lower left-hand corner, care being taken that the start is made straight with the eaves. The shingle point should be set back 2 or more inches, and nailed through the flange b. As each row is laid, the gable end flashings c should be attached as shown. The ridge is finished as shown at a, Fig. 54, and is put in place before the last tier of shingles is laid. In the case of a whole shingle not working and fitting into the grooves b of the ridge, it should be cut to the proper length.