Laying Off Common Rafter Seat Cut And End Cut. First Method: Having determined the rafter length as directed in Sec. 17, first method, (1) lay off this length along the upper edge beginning at the plumb cut. The whole number of feet is more safely "taken off " by means of a pole marked in feet, and of good length. The rule or square may be used to transmit fractional parts of a foot. (2) Place square as at "b," Fig. 52, standing as in Fig. 45-b, and scribe a plumb line as indicated at 1-2, Fig. 52. (3) From the point 1, Fig. 52, measure along the line marked 1-2 a distance equal to one-half that of 1-2. The distance 1-3 may be increased or decreased somewhat when an extreme pitch makes it advisable. As a rule this should be 2½" to 3". (4) Place the square as at c, Fig. 52, with the edge of the tongue resting on 3 and scribe a line for the seat cut, as 3-4. These last marks give the bird's mouth joint which is to fit over the plate.
Fig. 53. Independent Rafter Tail.
Fig. 54. Length of Ridge Piece.
While many carpenters allow end cutting of the rafter tails to wait until the rafters are set in place so that they may be lined and cut while in position, certain kinds of work permit the ends to be cut at the same time the remainder of the rafter is framed. In this latter method the square is placed as in Fig. 44 and (5) the end cut scribed. The point of cutoff on the tail is determined in the same manner as that used in determining rafter length, the run of the tail being considered and the tail length being measured from the point 1, Fig. 52.
Where a cornice is of unusual width, tails are usually framed independent of the rafters and are then spiked to the ends of the rafters either above or below the plate, Fig. 53.
Second Method: Where the second method of finding length, Section 17, is employed, the end cut and seat cut will be laid out before the plumb cut. The operator will stand as in Fig. 45-a.
When one rafter has been laid out it is cut and used as a pattern by which to cut similar rafters.