Figure 3-9. Steel carpenter's square
(2) Pattern Rafter Method. After the length has been determined, the timber is laid on
sawhorses (saw benches) with the crown or bow (if it has any) as the top side of the rafter. If possible,
select a straight piece for the pattern rafter. If a straight piece is not available, have the crown toward
the person laying out the rafter. Figure 3-10 illustrates the five steps of the pattern rafter method.
Hold the square with the tongue in the right hand, the blade in the left, and the heel
away from the body. Place the square as near the upper end of the rafter a possible.
In the example, the figure 8 on the tongue and 12 on the blade are placed along the
timber edge, that is to be the top edge of the rafter as shown in step 1. Mark along
the tongue edge of the square, which will be the plumb cut at the right.
Since the length of the rafter is known to be 12 feet 1/6 inch, measure the distance
from the top of the plumb cut and mark it on the timber. Hold the square in the
same manner with the 8 mark on the tongue directly over the 12-foot 1/6-inch mark.
Mark along the tongue of the square to give the plumb cut for the seat (see step 2).
Next, measure off perpendicular to this mark, the length of overhang along the
timber. Make a plumb-cut mark in the same way, keeping the square on the same
edge of the lumber (see step 3). This will be the tail cut of the rafter. Often, the tail
cut is made square across the timber.